RFE: Initial SIDs cannot be added or deleted without breaking compatibility #12
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As Eric Dumazet pointed out this also needs to be fixed in IPv6. v2: Contains the IPv6 tcp/Ipv6 dccp patches as well. We have seen a few incidents lately where a dst_enty has been freed with a dangling TCP socket reference (sk->sk_dst_cache) pointing to that dst_entry. If the conditions/timings are right a crash then ensues when the freed dst_entry is referenced later on. A Common crashing back trace is: #8 [] page_fault at ffffffff8163e648 [exception RIP: __tcp_ack_snd_check+74] . . #9 [] tcp_rcv_established at ffffffff81580b64 #10 [] tcp_v4_do_rcv at ffffffff8158b54a #11 [] tcp_v4_rcv at ffffffff8158cd02 #12 [] ip_local_deliver_finish at ffffffff815668f4 #13 [] ip_local_deliver at ffffffff81566bd9 #14 [] ip_rcv_finish at ffffffff8156656d #15 [] ip_rcv at ffffffff81566f06 #16 [] __netif_receive_skb_core at ffffffff8152b3a2 #17 [] __netif_receive_skb at ffffffff8152b608 #18 [] netif_receive_skb at ffffffff8152b690 #19 [] vmxnet3_rq_rx_complete at ffffffffa015eeaf [vmxnet3] #20 [] vmxnet3_poll_rx_only at ffffffffa015f32a [vmxnet3] #21 [] net_rx_action at ffffffff8152bac2 #22 [] __do_softirq at ffffffff81084b4f #23 [] call_softirq at ffffffff8164845c #24 [] do_softirq at ffffffff81016fc5 #25 [] irq_exit at ffffffff81084ee5 #26 [] do_IRQ at ffffffff81648ff8 Of course it may happen with other NIC drivers as well. It's found the freed dst_entry here: 224 static bool tcp_in_quickack_mode(struct sock *sk)↩ 225 {↩ 226 ▹ const struct inet_connection_sock *icsk = inet_csk(sk);↩ 227 ▹ const struct dst_entry *dst = __sk_dst_get(sk);↩ 228 ↩ 229 ▹ return (dst && dst_metric(dst, RTAX_QUICKACK)) ||↩ 230 ▹ ▹ (icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong);↩ 231 }↩ But there are other backtraces attributed to the same freed dst_entry in netfilter code as well. All the vmcores showed 2 significant clues: - Remote hosts behind the default gateway had always been redirected to a different gateway. A rtable/dst_entry will be added for that host. Making more dst_entrys with lower reference counts. Making this more probable. - All vmcores showed a postitive LockDroppedIcmps value, e.g: LockDroppedIcmps 267 A closer look at the tcp_v4_err() handler revealed that do_redirect() will run regardless of whether user space has the socket locked. This can result in a race condition where the same dst_entry cached in sk->sk_dst_entry can be decremented twice for the same socket via: do_redirect()->__sk_dst_check()-> dst_release(). Which leads to the dst_entry being prematurely freed with another socket pointing to it via sk->sk_dst_cache and a subsequent crash. To fix this skip do_redirect() if usespace has the socket locked. Instead let the redirect take place later when user space does not have the socket locked. The dccp/IPv6 code is very similar in this respect, so fixing it there too. As Eric Garver pointed out the following commit now invalidates routes. Which can set the dst->obsolete flag so that ipv4_dst_check() returns null and triggers the dst_release(). Fixes: ceb3320 ("ipv4: Kill routes during PMTU/redirect updates.") Cc: Eric Garver <egarver@redhat.com> Cc: Hannes Sowa <hsowa@redhat.com> Signed-off-by: Jon Maxwell <jmaxwell37@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
pcmoore
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This patch closes a long standing race in configfs between the creation of a new symlink in create_link(), while the symlink target's config_item is being concurrently removed via configfs_rmdir(). This can happen because the symlink target's reference is obtained by config_item_get() in create_link() before the CONFIGFS_USET_DROPPING bit set by configfs_detach_prep() during configfs_rmdir() shutdown is actually checked.. This originally manifested itself on ppc64 on v4.8.y under heavy load using ibmvscsi target ports with Novalink API: [ 7877.289863] rpadlpar_io: slot U8247.22L.212A91A-V1-C8 added [ 7879.893760] ------------[ cut here ]------------ [ 7879.893768] WARNING: CPU: 15 PID: 17585 at ./include/linux/kref.h:46 config_item_get+0x7c/0x90 [configfs] [ 7879.893811] CPU: 15 PID: 17585 Comm: targetcli Tainted: G O 4.8.17-customv2.22 #12 [ 7879.893812] task: c00000018a0d3400 task.stack: c0000001f3b40000 [ 7879.893813] NIP: d000000002c664ec LR: d000000002c60980 CTR: c000000000b70870 [ 7879.893814] REGS: c0000001f3b43810 TRAP: 0700 Tainted: G O (4.8.17-customv2.22) [ 7879.893815] MSR: 8000000000029033 <SF,EE,ME,IR,DR,RI,LE> CR: 28222242 XER: 00000000 [ 7879.893820] CFAR: d000000002c664bc SOFTE: 1 GPR00: d000000002c60980 c0000001f3b43a90 d000000002c70908 c0000000fbc06820 GPR04: c0000001ef1bd900 0000000000000004 0000000000000001 0000000000000000 GPR08: 0000000000000000 0000000000000001 d000000002c69560 d000000002c66d80 GPR12: c000000000b70870 c00000000e798700 c0000001f3b43ca0 c0000001d4949d40 GPR16: c00000014637e1c0 0000000000000000 0000000000000000 c0000000f2392940 GPR20: c0000001f3b43b98 0000000000000041 0000000000600000 0000000000000000 GPR24: fffffffffffff000 0000000000000000 d000000002c60be0 c0000001f1dac490 GPR28: 0000000000000004 0000000000000000 c0000001ef1bd900 c0000000f2392940 [ 7879.893839] NIP [d000000002c664ec] config_item_get+0x7c/0x90 [configfs] [ 7879.893841] LR [d000000002c60980] check_perm+0x80/0x2e0 [configfs] [ 7879.893842] Call Trace: [ 7879.893844] [c0000001f3b43ac0] [d000000002c60980] check_perm+0x80/0x2e0 [configfs] [ 7879.893847] [c0000001f3b43b10] [c000000000329770] do_dentry_open+0x2c0/0x460 [ 7879.893849] [c0000001f3b43b70] [c000000000344480] path_openat+0x210/0x1490 [ 7879.893851] [c0000001f3b43c80] [c00000000034708c] do_filp_open+0xfc/0x170 [ 7879.893853] [c0000001f3b43db0] [c00000000032b5bc] do_sys_open+0x1cc/0x390 [ 7879.893856] [c0000001f3b43e30] [c000000000009584] system_call+0x38/0xec [ 7879.893856] Instruction dump: [ 7879.893858] 409d0014 38210030 e8010010 7c0803a6 4e800020 3d220000 e94981e0 892a0000 [ 7879.893861] 2f890000 409effe0 39200001 992a0000 <0fe00000> 4bffffd0 60000000 60000000 [ 7879.893866] ---[ end trace 14078f0b3b5ad0aa ]--- To close this race, go ahead and obtain the symlink's target config_item reference only after the existing CONFIGFS_USET_DROPPING check succeeds. This way, if configfs_rmdir() wins create_link() will return -ENONET, and if create_link() wins configfs_rmdir() will return -EBUSY. Reported-by: Bryant G. Ly <bryantly@linux.vnet.ibm.com> Tested-by: Bryant G. Ly <bryantly@linux.vnet.ibm.com> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org> Signed-off-by: Christoph Hellwig <hch@lst.de> Cc: stable@vger.kernel.org
pcmoore
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Oct 22, 2018
Adding to tests that aims on kernel breakpoint modification bugs. First test creates HW breakpoint, tries to change it and checks it was properly changed. It aims on kernel issue that prevents HW breakpoint to be changed via ptrace interface. The first test forks, the child sets itself as ptrace tracee and waits in signal for parent to trace it, then it calls bp_1 and quits. The parent does following steps: - creates a new breakpoint (id 0) for bp_2 function - changes that breakpoint to bp_1 function - waits for the breakpoint to hit and checks it has proper rip of bp_1 function This test aims on an issue in kernel preventing to change disabled breakpoints Second test mimics the first one except for few steps in the parent: - creates a new breakpoint (id 0) for bp_1 function - changes that breakpoint to bogus (-1) address - waits for the breakpoint to hit and checks it has proper rip of bp_1 function This test aims on an issue in kernel disabling enabled breakpoint after unsuccesful change. Committer testing: # uname -a Linux jouet 4.18.0-rc8-00002-g1236568ee3cb #12 SMP Tue Aug 7 14:08:26 -03 2018 x86_64 x86_64 x86_64 GNU/Linux # perf test -v "bp modify" 62: x86 bp modify : --- start --- test child forked, pid 25671 in bp_1 tracee exited prematurely 2 FAILED arch/x86/tests/bp-modify.c:209 modify test 1 failed test child finished with -1 ---- end ---- x86 bp modify: FAILED! # Signed-off-by: Jiri Olsa <jolsa@kernel.org> Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: David Ahern <dsahern@gmail.com> Cc: Milind Chabbi <chabbi.milind@gmail.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20180827091228.2878-2-jolsa@kernel.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
stephensmalley
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Jan 27, 2020
Remove initial SIDs that have never been used or are no longer used by the kernel from its string table, which is also used to generate the SECINITSID_* symbols referenced in code. Update the code to gracefully handle the fact that these can now be NULL. Stop treating it as an error if a policy defines additional initial SIDs unknown to the kernel, or if the policy leaves one of the unused initial SIDs without a defined context. Fix the incorrect usage of the name from the ocontext in error messages when loading initial SIDs since these are not presently written to the kernel policy and are therefore always NULL. This is a first step toward enabling future evolution of initial SIDs. Further changes are required to both userspace and the kernel to fully address SELinuxProject#12 but this takes a small step toward that end. NB Even with this change, one cannot yet add or remove initial SIDs in policy without breakage; separate changes to the policy compiler are still necessary. Further, fully decoupling the policy and kernel initial SID values will require a policy format/version change to include the SID names in the kernel policy so that they can be dynamically mapped at policy load. Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
stephensmalley
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Jan 29, 2020
Remove initial SIDs that have never been used or are no longer used by the kernel from its string table, which is also used to generate the SECINITSID_* symbols referenced in code. Update the code to gracefully handle the fact that these can now be NULL. Stop treating it as an error if a policy defines additional initial SIDs unknown to the kernel. Do not load unused initial SID contexts into the sidtab. Fix the incorrect usage of the name from the ocontext in error messages when loading initial SIDs since these are not presently written to the kernel policy and are therefore always NULL. This is a first step toward enabling future evolution of initial SIDs. Further changes are required to both userspace and the kernel to fully address SELinuxProject#12 but this takes a small step toward that end. Fully decoupling the policy and kernel initial SID values will require introducing a mapping between them and dyhamically mapping them at load time. Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
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If/when "selinux: remove unused initial SIDs and improve handling" is merged, it will be possible to reclaim and reuse any of the unused initial SIDs in future kernels without compatibility issues so long as refpolicy wasn't assigning them a context other than unlabeled. Only the "fs" SID (4) and "sysctl" SID (17) appear to have still been assigned contexts other than unlabeled, so those two should probably be left unused by the kernel (unless the desired context happens to coincide) but the other unused initial SIDs should be reusable if needed. Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately became a fatal error in 24ed7fd (v5.0) and even before that it could cause problems on a policy reload (collision between the new initial SID and a SID allocated at runtime) ever since 42596ea (v2.6.34) so we cannot safely start adding new initial SIDs beyond SECINITSID_NUM (27) until such a time as all such kernels are dead and gone and only those that include this patch are relevant. That is probably not a big deal since we haven't added a new initial SID since 2004 (v2.6.7) and we have plenty of unused ones we can reclaim if we truly need one. If we want to avoid the wasted storage in initial_sid_to_string[] and/or sidtab->isids[] for the unused initial SIDs, we could introduce an indirection between the kernel initial SID values and the policy initial SID values and just map the policy SID values in the ocontexts to the kernel values during policy_load_isids(). Originally I thought we'd do this by preserving the initial SID names in the kernel policy and creating a mapping at load time like we do for the security classes and permissions but that would require a new kernel policy format version and associated changes to libsepol/checkpolicy and I'm not sure it is justified. Simpler approach is just to create a fixed mapping table in the kernel from the existing fixed policy values to the kernel values. Less flexible but probably sufficient. With the recently posted patch for libsepol,checkpolicy to support omitting initial SID contexts, it will be possible to start dropping the unused initial SID contexts from future policies without breaking compatibility even with kernels that precede this patch. Again, the "fs" and "sysctl" SID contexts will need to remain but the rest can go. The initial SID declarations themselves will remain to preserve the values of the subsequent ones but the contexts can be dropped. If/when the kernel decides to reuse one of them, future policies can change the name and start assigning them a context without breaking compatibility. Given this, I'm inclined to close this issue once the aforementioned kernel and libsepol,checkpolicy patches are merged since I think they provide as much flexibility as we are likely to get/need in the near term and more will have to wait on kernels that predate this change being obsoleted. Full dynamic initial SID mapping support is probably not justified until/unless we start to see more use of initial SIDs. |
I'm a little confused @stephensmalley, reference policy defines a handful of initial sids something other than unlabeled? What am I missing or confusing in your statement above? |
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Of the initial SIDs unused by kernel code (i.e. no usage of SECINITSID_name in code anywhere beyond the generated #define), only the "fs" (4) and "sysctl" (17) SIDs were still being defined contexts other than unlabeled in refpolicy (not overly concerned about mls policies, so ignoring the mls field). The unused initial SIDs that are safely reclaimable are "file_labels" (6), "init" (7), "igmp_packet" (13), "icmp_socket" (14), "tcp_socket" (15), "sysctl_modprobe" (16), "sysctl_fs" (18) through "scmp_packet" (26). These were never used in any upstream kernel. If we are worried about full compatibility of future kernels with existing mls policies, then I guess the safely reclaimable set are just those that have unlabeled_t and mls_systemhigh i.e. same as sid unlabeled, which would be "icmp_socket", "igmp_packet", kmod", "policy", "scmp_packet", "tcp_socket". |
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Here is how I would envision staging changes to the initial SIDs in a compatible manner:
I don't expect to still be working by the time we reach the end of the above... |
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One other addendum: there is one initial SID under the "These initial sids are no longer used" comment in refpolicy that actually is in use today ("any_socket"); it was revived in d28d1e0 (v2.6.16) as part of the labeled IPSEC changes. So that one shouldn't be dropped from refpolicy. |
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libsepol support for omitting unused initial SID contexts was merged in SELinuxProject/selinux@8677ce5 |
pcmoore
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Remove initial SIDs that have never been used or are no longer used by the kernel from its string table, which is also used to generate the SECINITSID_* symbols referenced in code. Update the code to gracefully handle the fact that these can now be NULL. Stop treating it as an error if a policy defines additional initial SIDs unknown to the kernel. Do not load unused initial SID contexts into the sidtab. Fix the incorrect usage of the name from the ocontext in error messages when loading initial SIDs since these are not presently written to the kernel policy and are therefore always NULL. After this change, it is possible to safely reclaim and reuse some of the unused initial SIDs without compatibility issues. Specifically, unused initial SIDs that were being assigned the same context as the unlabeled initial SID in policies can be reclaimed and reused for another purpose, with existing policies still treating them as having the unlabeled context and future policies having the option of mapping them to a more specific context. For example, this could have been used when the infiniband labeling support was introduced to define initial SIDs for the default pkey and endport SIDs similar to the handling of port/netif/node SIDs rather than always using SECINITSID_UNLABELED as the default. The set of safely reclaimable unused initial SIDs across all known policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod (24), policy (25), and scmp_packet (26); these initial SIDs were assigned the same context as unlabeled in all known policies including mls. If only considering non-mls policies (i.e. assuming that mls users always upgrade policy with their kernels), the set of safely reclaimable unused initial SIDs further includes file_labels (6), init (7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23). Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately became a fatal error in commit 24ed7fd ("selinux: use separate table for initial SID lookup") and even before that it could cause problems on a policy reload (collision between the new initial SID and one allocated at runtime) ever since commit 42596ea ("selinux: load the initial SIDs upon every policy load") so we cannot safely start adding new initial SIDs to policies beyond SECINITSID_NUM (27) until such a time as all such kernels do not need to be supported and only those that include this commit are relevant. That is not a big deal since we haven't added a new initial SID since 2004 (v2.6.7) and we have plenty of unused ones we can reclaim if we truly need one. If we want to avoid the wasted storage in initial_sid_to_string[] and/or sidtab->isids[] for the unused initial SIDs, we could introduce an indirection between the kernel initial SID values and the policy initial SID values and just map the policy SID values in the ocontexts to the kernel values during policy_load_isids(). Originally I thought we'd do this by preserving the initial SID names in the kernel policy and creating a mapping at load time like we do for the security classes and permissions but that would require a new kernel policy format version and associated changes to libsepol/checkpolicy and I'm not sure it is justified. Simpler approach is just to create a fixed mapping table in the kernel from the existing fixed policy values to the kernel values. Less flexible but probably sufficient. A separate selinux userspace change was applied in SELinuxProject/selinux@8677ce5 to enable removal of most of the unused initial SID contexts from policies, but there is no dependency between that change and this one. That change permits removing all of the unused initial SID contexts from policy except for the fs and sysctl SID contexts. The initial SID declarations themselves would remain in policy to preserve the values of subsequent ones but the contexts can be dropped. If/when the kernel decides to reuse one of them, future policies can change the name and start assigning a context again without breaking compatibility. Here is how I would envision staging changes to the initial SIDs in a compatible manner after this commit is applied: 1. At any time after this commit is applied, the kernel could choose to reclaim one of the safely reclaimable unused initial SIDs listed above for a new purpose (i.e. replace its NULL entry in the initial_sid_to_string[] table with a new name and start using the newly generated SECINITSID_name symbol in code), and refpolicy could at that time rename its declaration of that initial SID to reflect its new purpose and start assigning it a context going forward. Existing/old policies would map the reclaimed initial SID to the unlabeled context, so that would be the initial default behavior until policies are updated. This doesn't depend on the selinux userspace change; it will work with existing policies and userspace. 2. In 6 months or so we'll have another SELinux userspace release that will include the libsepol/checkpolicy support for omitting unused initial SID contexts. 3. At any time after that release, refpolicy can make that release its minimum build requirement and drop the sid context statements (but not the sid declarations) for all of the unused initial SIDs except for fs and sysctl, which must remain for compatibility on policy reload with old kernels and for compatibility with kernels that were still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this kernel commit; it will work with previous kernels as well. 4. After N years for some value of N, refpolicy decides that it no longer cares about policy reload compatibility for kernels that predate this kernel commit, and refpolicy drops the fs and sysctl SID contexts from policy too (but retains the declarations). 5. After M years for some value of M, the kernel decides that it no longer cares about compatibility with refpolicies that predate step 4 (dropping the fs and sysctl SIDs), and those two SIDs also become safely reclaimable. This step is optional and need not ever occur unless we decide that the need to reclaim those two SIDs outweighs the compatibility cost. 6. After O years for some value of O, refpolicy decides that it no longer cares about policy load (not just reload) compatibility for kernels that predate this kernel commit, and both kernel and refpolicy can then start adding and using new initial SIDs beyond 27. This does not depend on the previous change (step 5) and can occur independent of it. Fixes: #12 Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov> Signed-off-by: Paul Moore <paul@paul-moore.com>
hohoxu
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Apr 1, 2020
Remove initial SIDs that have never been used or are no longer used by the kernel from its string table, which is also used to generate the SECINITSID_* symbols referenced in code. Update the code to gracefully handle the fact that these can now be NULL. Stop treating it as an error if a policy defines additional initial SIDs unknown to the kernel. Do not load unused initial SID contexts into the sidtab. Fix the incorrect usage of the name from the ocontext in error messages when loading initial SIDs since these are not presently written to the kernel policy and are therefore always NULL. After this change, it is possible to safely reclaim and reuse some of the unused initial SIDs without compatibility issues. Specifically, unused initial SIDs that were being assigned the same context as the unlabeled initial SID in policies can be reclaimed and reused for another purpose, with existing policies still treating them as having the unlabeled context and future policies having the option of mapping them to a more specific context. For example, this could have been used when the infiniband labeling support was introduced to define initial SIDs for the default pkey and endport SIDs similar to the handling of port/netif/node SIDs rather than always using SECINITSID_UNLABELED as the default. The set of safely reclaimable unused initial SIDs across all known policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod (24), policy (25), and scmp_packet (26); these initial SIDs were assigned the same context as unlabeled in all known policies including mls. If only considering non-mls policies (i.e. assuming that mls users always upgrade policy with their kernels), the set of safely reclaimable unused initial SIDs further includes file_labels (6), init (7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23). Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately became a fatal error in commit 24ed7fd ("selinux: use separate table for initial SID lookup") and even before that it could cause problems on a policy reload (collision between the new initial SID and one allocated at runtime) ever since commit 42596ea ("selinux: load the initial SIDs upon every policy load") so we cannot safely start adding new initial SIDs to policies beyond SECINITSID_NUM (27) until such a time as all such kernels do not need to be supported and only those that include this commit are relevant. That is not a big deal since we haven't added a new initial SID since 2004 (v2.6.7) and we have plenty of unused ones we can reclaim if we truly need one. If we want to avoid the wasted storage in initial_sid_to_string[] and/or sidtab->isids[] for the unused initial SIDs, we could introduce an indirection between the kernel initial SID values and the policy initial SID values and just map the policy SID values in the ocontexts to the kernel values during policy_load_isids(). Originally I thought we'd do this by preserving the initial SID names in the kernel policy and creating a mapping at load time like we do for the security classes and permissions but that would require a new kernel policy format version and associated changes to libsepol/checkpolicy and I'm not sure it is justified. Simpler approach is just to create a fixed mapping table in the kernel from the existing fixed policy values to the kernel values. Less flexible but probably sufficient. A separate selinux userspace change was applied in SELinuxProject/selinux@8677ce5 to enable removal of most of the unused initial SID contexts from policies, but there is no dependency between that change and this one. That change permits removing all of the unused initial SID contexts from policy except for the fs and sysctl SID contexts. The initial SID declarations themselves would remain in policy to preserve the values of subsequent ones but the contexts can be dropped. If/when the kernel decides to reuse one of them, future policies can change the name and start assigning a context again without breaking compatibility. Here is how I would envision staging changes to the initial SIDs in a compatible manner after this commit is applied: 1. At any time after this commit is applied, the kernel could choose to reclaim one of the safely reclaimable unused initial SIDs listed above for a new purpose (i.e. replace its NULL entry in the initial_sid_to_string[] table with a new name and start using the newly generated SECINITSID_name symbol in code), and refpolicy could at that time rename its declaration of that initial SID to reflect its new purpose and start assigning it a context going forward. Existing/old policies would map the reclaimed initial SID to the unlabeled context, so that would be the initial default behavior until policies are updated. This doesn't depend on the selinux userspace change; it will work with existing policies and userspace. 2. In 6 months or so we'll have another SELinux userspace release that will include the libsepol/checkpolicy support for omitting unused initial SID contexts. 3. At any time after that release, refpolicy can make that release its minimum build requirement and drop the sid context statements (but not the sid declarations) for all of the unused initial SIDs except for fs and sysctl, which must remain for compatibility on policy reload with old kernels and for compatibility with kernels that were still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this kernel commit; it will work with previous kernels as well. 4. After N years for some value of N, refpolicy decides that it no longer cares about policy reload compatibility for kernels that predate this kernel commit, and refpolicy drops the fs and sysctl SID contexts from policy too (but retains the declarations). 5. After M years for some value of M, the kernel decides that it no longer cares about compatibility with refpolicies that predate step 4 (dropping the fs and sysctl SIDs), and those two SIDs also become safely reclaimable. This step is optional and need not ever occur unless we decide that the need to reclaim those two SIDs outweighs the compatibility cost. 6. After O years for some value of O, refpolicy decides that it no longer cares about policy load (not just reload) compatibility for kernels that predate this kernel commit, and both kernel and refpolicy can then start adding and using new initial SIDs beyond 27. This does not depend on the previous change (step 5) and can occur independent of it. Fixes: SELinuxProject/selinux-kernel#12 Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov> Signed-off-by: Paul Moore <paul@paul-moore.com>
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Fixed via e3e0b58. |
FYI, the master branch is updated, but only when there is a new tagged release from Linus. If you look at it now you will see it is based on v5.6. |
0wnerDied
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Sep 19, 2020
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fdae669 ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: atndko <z1281552865@gmail.com>
0wnerDied
pushed a commit
to 0wnerDied/Neptune_kernel_sm8150_oneplus
that referenced
this issue
Oct 4, 2020
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fdae669 ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Park Ju Hyung <qkrwngud825@gmail.com>
Signed-off-by: atndko <z1281552865@gmail.com>
0wnerDied
pushed a commit
to 0wnerDied/Neptune_kernel_sm8150_oneplus
that referenced
this issue
Oct 4, 2020
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fdae669 ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Park Ju Hyung <qkrwngud825@gmail.com>
Signed-off-by: atndko <z1281552865@gmail.com>
0ctobot
pushed a commit
to 0ctobot/neutrino_kernel_oneplus_sm8150
that referenced
this issue
Oct 5, 2020
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fdae669 ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Park Ju Hyung <qkrwngud825@gmail.com>
0ctobot
pushed a commit
to 0ctobot/neutrino_kernel_oneplus_sm8150
that referenced
this issue
Oct 6, 2020
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fdae669 ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Adam W. Willis <return.of.octobot@gmail.com>
0ctobot
pushed a commit
to 0ctobot/neutrino_kernel_oneplus_sm8150
that referenced
this issue
Oct 6, 2020
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fdae669 ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Adam W. Willis <return.of.octobot@gmail.com>
idkwhoiam322
pushed a commit
to idkwhoiam322/weeb_kernel_oneplus_sm8150
that referenced
this issue
Oct 6, 2020
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fdae669 ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Park Ju Hyung <qkrwngud825@gmail.com>
nem0-z
pushed a commit
to nem0-z/android_kernel_oneplus_sm8150
that referenced
this issue
Oct 10, 2020
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fdae669 ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Adam W. Willis <return.of.octobot@gmail.com>
aruato
pushed a commit
to aruato/moob
that referenced
this issue
Oct 10, 2020
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fdae669 ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Park Ju Hyung <qkrwngud825@gmail.com>
aruato
pushed a commit
to aruato/moob
that referenced
this issue
Oct 10, 2020
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fdae669 ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Park Ju Hyung <qkrwngud825@gmail.com>
nem0-z
pushed a commit
to nem0-z/android_kernel_oneplus_sm8150
that referenced
this issue
Oct 11, 2020
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fdae669 ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Adam W. Willis <return.of.octobot@gmail.com>
Reinazhard
pushed a commit
to Reinazhard/android_kernel_xiaomi_whyred
that referenced
this issue
Jul 8, 2022
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fdae669 ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Reinazhard
pushed a commit
to Reinazhard/android_kernel_xiaomi_whyred
that referenced
this issue
Jul 8, 2022
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fdae669 ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Reinazhard
pushed a commit
to Reinazhard/android_kernel_xiaomi_whyred
that referenced
this issue
Jul 8, 2022
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fdae669 ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Reinazhard <reinazhard@gmail.com>
pcmoore
pushed a commit
that referenced
this issue
Aug 15, 2022
Since commit 6493792 ("ext4: convert symlink external data block mapping to bdev"), create new symlink with inline_data is not supported, but it missing to handle the leftover inlined symlinks, which could cause below error message and fail to read symlink. ls: cannot read symbolic link 'foo': Structure needs cleaning EXT4-fs error (device sda): ext4_map_blocks:605: inode #12: block 2021161080: comm ls: lblock 0 mapped to illegal pblock 2021161080 (length 1) Fix this regression by adding ext4_read_inline_link(), which read the inline data directly and convert it through a kmalloced buffer. Fixes: 6493792 ("ext4: convert symlink external data block mapping to bdev") Cc: stable@kernel.org Reported-by: Torge Matthies <openglfreak@googlemail.com> Signed-off-by: Zhang Yi <yi.zhang@huawei.com> Tested-by: Torge Matthies <openglfreak@googlemail.com> Link: https://lore.kernel.org/r/20220630090100.2769490-1-yi.zhang@huawei.com Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reinazhard
pushed a commit
to Reinazhard/android_kernel_xiaomi_whyred
that referenced
this issue
Aug 23, 2022
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fdae669 ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Reinazhard <reinazhard@gmail.com>
Reinazhard
pushed a commit
to Reinazhard/android_kernel_xiaomi_whyred
that referenced
this issue
Aug 23, 2022
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fdae669 ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Reinazhard <reinazhard@gmail.com>
Reinazhard
pushed a commit
to Reinazhard/android_kernel_xiaomi_whyred
that referenced
this issue
Nov 5, 2022
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fdae669 ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Reinazhard <reinazhard@gmail.com>
Reinazhard
pushed a commit
to Reinazhard/android_kernel_xiaomi_whyred
that referenced
this issue
Nov 5, 2022
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fdae669 ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Reinazhard <reinazhard@gmail.com>
Reinazhard
pushed a commit
to Reinazhard/android_kernel_xiaomi_whyred
that referenced
this issue
Nov 5, 2022
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fdae669 ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Reinazhard <reinazhard@gmail.com>
Reinazhard
pushed a commit
to Reinazhard/android_kernel_xiaomi_whyred
that referenced
this issue
Nov 5, 2022
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fdae669 ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Reinazhard <reinazhard@gmail.com>
Reinazhard
pushed a commit
to Reinazhard/android_kernel_xiaomi_whyred
that referenced
this issue
Dec 6, 2022
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fdae669 ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Reinazhard <reinazhard@gmail.com>
pcmoore
pushed a commit
that referenced
this issue
Jan 3, 2023
Ido Schimmel says:
====================
bridge: mcast: Extensions for EVPN
tl;dr
=====
This patchset creates feature parity between user space and the kernel
and allows the former to install and replace MDB port group entries with
a source list and associated filter mode. This is required for EVPN use
cases where multicast state is not derived from snooped IGMP/MLD
packets, but instead derived from EVPN routes exchanged by the control
plane in user space.
Background
==========
IGMPv3 [1] and MLDv2 [2] differ from earlier versions of the protocols
in that they add support for source-specific multicast. That is, hosts
can advertise interest in listening to a particular multicast address
only from specific source addresses or from all sources except for
specific source addresses.
In kernel 5.10 [3][4], the bridge driver gained the ability to snoop
IGMPv3/MLDv2 packets and install corresponding MDB port group entries.
For example, a snooped IGMPv3 Membership Report that contains a single
MODE_IS_EXCLUDE record for group 239.10.10.10 with sources 192.0.2.1,
192.0.2.2, 192.0.2.20 and 192.0.2.21 would trigger the creation of these
entries:
# bridge -d mdb show
dev br0 port veth1 grp 239.10.10.10 src 192.0.2.21 temp filter_mode include proto kernel blocked
dev br0 port veth1 grp 239.10.10.10 src 192.0.2.20 temp filter_mode include proto kernel blocked
dev br0 port veth1 grp 239.10.10.10 src 192.0.2.2 temp filter_mode include proto kernel blocked
dev br0 port veth1 grp 239.10.10.10 src 192.0.2.1 temp filter_mode include proto kernel blocked
dev br0 port veth1 grp 239.10.10.10 temp filter_mode exclude source_list 192.0.2.21/0.00,192.0.2.20/0.00,192.0.2.2/0.00,192.0.2.1/0.00 proto kernel
While the kernel can install and replace entries with a filter mode and
source list, user space cannot. It can only add EXCLUDE entries with an
empty source list, which is sufficient for IGMPv2/MLDv1, but not for
IGMPv3/MLDv2.
Use cases where the multicast state is not derived from snooped packets,
but instead derived from routes exchanged by the user space control
plane require feature parity between user space and the kernel in terms
of MDB configuration. Such a use case is detailed in the next section.
Motivation
==========
RFC 7432 [5] defines a "MAC/IP Advertisement route" (type 2) [6] that
allows NVE switches in the EVPN network to advertise and learn
reachability information for unicast MAC addresses. Traffic destined to
a unicast MAC address can therefore be selectively forwarded to a single
NVE switch behind which the MAC is located.
The same is not true for IP multicast traffic. Such traffic is simply
flooded as BUM to all NVE switches in the broadcast domain (BD),
regardless if a switch has interested receivers for the multicast stream
or not. This is especially problematic for overlay networks that make
heavy use of multicast.
The issue is addressed by RFC 9251 [7] that defines a "Selective
Multicast Ethernet Tag Route" (type 6) [8] which allows NVE switches in
the EVPN network to advertise multicast streams that they are interested
in. This is done by having each switch suppress IGMP/MLD packets from
being transmitted to the NVE network and instead communicate the
information over BGP to other switches.
As far as the bridge driver is concerned, the above means that the
multicast state (i.e., {multicast address, group timer, filter-mode,
(source records)}) for the VXLAN bridge port is not populated by the
kernel from snooped IGMP/MLD packets (they are suppressed), but instead
by user space. Specifically, by the routing daemon that is exchanging
EVPN routes with other NVE switches.
Changes are obviously also required in the VXLAN driver, but they are
the subject of future patchsets. See the "Future work" section.
Implementation
==============
The user interface is extended to allow user space to specify the filter
mode of the MDB port group entry and its source list. Replace support is
also added so that user space would not need to remove an entry and
re-add it only to edit its source list or filter mode, as that would
result in packet loss. Example usage:
# bridge mdb replace dev br0 port dummy10 grp 239.1.1.1 permanent \
source_list 192.0.2.1,192.0.2.3 filter_mode exclude proto zebra
# bridge -d -s mdb show
dev br0 port dummy10 grp 239.1.1.1 src 192.0.2.3 permanent filter_mode include proto zebra blocked 0.00
dev br0 port dummy10 grp 239.1.1.1 src 192.0.2.1 permanent filter_mode include proto zebra blocked 0.00
dev br0 port dummy10 grp 239.1.1.1 permanent filter_mode exclude source_list 192.0.2.3/0.00,192.0.2.1/0.00 proto zebra 0.00
The netlink interface is extended with a few new attributes in the
RTM_NEWMDB request message:
[ struct nlmsghdr ]
[ struct br_port_msg ]
[ MDBA_SET_ENTRY ]
struct br_mdb_entry
[ MDBA_SET_ENTRY_ATTRS ]
[ MDBE_ATTR_SOURCE ]
struct in_addr / struct in6_addr
[ MDBE_ATTR_SRC_LIST ] // new
[ MDBE_SRC_LIST_ENTRY ]
[ MDBE_SRCATTR_ADDRESS ]
struct in_addr / struct in6_addr
[ ...]
[ MDBE_ATTR_GROUP_MODE ] // new
u8
[ MDBE_ATTR_RTPORT ] // new
u8
No changes are required in RTM_NEWMDB responses and notifications, as
all the information can already be dumped by the kernel today.
Testing
=======
Tested with existing bridge multicast selftests: bridge_igmp.sh,
bridge_mdb_port_down.sh, bridge_mdb.sh, bridge_mld.sh,
bridge_vlan_mcast.sh.
In addition, added many new test cases for existing as well as for new
MDB functionality.
Patchset overview
=================
Patches #1-#8 are non-functional preparations for the core changes in
later patches.
Patches #9-#10 allow user space to install (*, G) entries with a source
list and associated filter mode. Specifically, patch #9 adds the
necessary kernel plumbing and patch #10 exposes the new functionality to
user space via a few new attributes.
Patch #11 allows user space to specify the routing protocol of new MDB
port group entries so that a routing daemon could differentiate between
entries installed by it and those installed by an administrator.
Patch #12 allows user space to replace MDB port group entries. This is
useful, for example, when user space wants to add a new source to a
source list. Instead of deleting a (*, G) entry and re-adding it with an
extended source list (which would result in packet loss), user space can
simply replace the current entry.
Patches #13-#14 add tests for existing MDB functionality as well as for
all new functionality added in this patchset.
Future work
===========
The VXLAN driver will need to be extended with an MDB so that it could
selectively forward IP multicast traffic to NVE switches with interested
receivers instead of simply flooding it to all switches as BUM.
The idea is to reuse the existing MDB interface for the VXLAN driver in
a similar way to how the FDB interface is shared between the bridge and
VXLAN drivers.
From command line perspective, configuration will look as follows:
# bridge mdb add dev br0 port vxlan0 grp 239.1.1.1 permanent \
filter_mode exclude source_list 198.50.100.1,198.50.100.2
# bridge mdb add dev vxlan0 port vxlan0 grp 239.1.1.1 permanent \
filter_mode include source_list 198.50.100.3,198.50.100.4 \
dst 192.0.2.1 dst_port 4789 src_vni 2
# bridge mdb add dev vxlan0 port vxlan0 grp 239.1.1.1 permanent \
filter_mode exclude source_list 198.50.100.1,198.50.100.2 \
dst 192.0.2.2 dst_port 4789 src_vni 2
Where the first command is enabled by this set, but the next two will be
the subject of future work.
From netlink perspective, the existing PF_BRIDGE/RTM_*MDB messages will
be extended to the VXLAN driver. This means that a few new attributes
will be added (e.g., 'MDBE_ATTR_SRC_VNI') and that the handlers for
these messages will need to move to net/core/rtnetlink.c. The rtnetlink
code will call into the appropriate driver based on the ifindex
specified in the ancillary header.
iproute2 patches can be found here [9].
Changelog
=========
Since v1 [10]:
* Patch #12: Remove extack from br_mdb_replace_group_sg().
* Patch #12: Change 'nlflags' to u16 and move it after 'filter_mode' to
pack the structure.
Since RFC [11]:
* Patch #6: New patch.
* Patch #9: Use an array instead of a list to store source entries.
* Patch #10: Use an array instead of list to store source entries.
* Patch #10: Drop br_mdb_config_attrs_fini().
* Patch #11: Reject protocol for host entries.
* Patch #13: New patch.
* Patch #14: New patch.
[1] https://datatracker.ietf.org/doc/html/rfc3376
[2] https://www.rfc-editor.org/rfc/rfc3810
[3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6af52ae2ed14a6bc756d5606b29097dfd76740b8
[4] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=68d4fd30c83b1b208e08c954cd45e6474b148c87
[5] https://datatracker.ietf.org/doc/html/rfc7432
[6] https://datatracker.ietf.org/doc/html/rfc7432#section-7.2
[7] https://datatracker.ietf.org/doc/html/rfc9251
[8] https://datatracker.ietf.org/doc/html/rfc9251#section-9.1
[9] https://github.com/idosch/iproute2/commits/submit/mdb_v1
[10] https://lore.kernel.org/netdev/20221208152839.1016350-1-idosch@nvidia.com/
[11] https://lore.kernel.org/netdev/20221018120420.561846-1-idosch@nvidia.com/
====================
Link: https://lore.kernel.org/r/20221210145633.1328511-1-idosch@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
pcmoore
pushed a commit
that referenced
this issue
Jan 3, 2023
We need to check if we have a OS prefix, otherwise we stumble on a
metric segv that I'm now seeing in Arnaldo's tree:
$ gdb --args perf stat -M Backend true
...
Performance counter stats for 'true':
4,712,355 TOPDOWN.SLOTS # 17.3 % tma_core_bound
Program received signal SIGSEGV, Segmentation fault.
__strlen_evex () at ../sysdeps/x86_64/multiarch/strlen-evex.S:77
77 ../sysdeps/x86_64/multiarch/strlen-evex.S: No such file or directory.
(gdb) bt
#0 __strlen_evex () at ../sysdeps/x86_64/multiarch/strlen-evex.S:77
#1 0x00007ffff74749a5 in __GI__IO_fputs (str=0x0, fp=0x7ffff75f5680 <_IO_2_1_stderr_>)
#2 0x0000555555779f28 in do_new_line_std (config=0x555555e077c0 <stat_config>, os=0x7fffffffbf10) at util/stat-display.c:356
#3 0x000055555577a081 in print_metric_std (config=0x555555e077c0 <stat_config>, ctx=0x7fffffffbf10, color=0x0, fmt=0x5555558b77b5 "%8.1f", unit=0x7fffffffbb10 "% tma_memory_bound", val=13.165355724442199) at util/stat-display.c:380
#4 0x00005555557768b6 in generic_metric (config=0x555555e077c0 <stat_config>, metric_expr=0x55555593d5b7 "((CYCLE_ACTIVITY.STALLS_MEM_ANY + EXE_ACTIVITY.BOUND_ON_STORES) / (CYCLE_ACTIVITY.STALLS_TOTAL + (EXE_ACTIVITY.1_PORTS_UTIL + tma_retiring * EXE_ACTIVITY.2_PORTS_UTIL) + EXE_ACTIVITY.BOUND_ON_STORES))"..., metric_events=0x555555f334e0, metric_refs=0x555555ec81d0, name=0x555555f32e80 "TOPDOWN.SLOTS", metric_name=0x555555f26c80 "tma_memory_bound", metric_unit=0x55555593d5b1 "100%", runtime=0, map_idx=0, out=0x7fffffffbd90, st=0x555555e9e620 <rt_stat>) at util/stat-shadow.c:934
#5 0x0000555555778cac in perf_stat__print_shadow_stats (config=0x555555e077c0 <stat_config>, evsel=0x555555f289d0, avg=4712355, map_idx=0, out=0x7fffffffbd90, metric_events=0x555555e078e8 <stat_config+296>, st=0x555555e9e620 <rt_stat>) at util/stat-shadow.c:1329
#6 0x000055555577b6a0 in printout (config=0x555555e077c0 <stat_config>, os=0x7fffffffbf10, uval=4712355, run=325322, ena=325322, noise=4712355, map_idx=0) at util/stat-display.c:741
#7 0x000055555577bc74 in print_counter_aggrdata (config=0x555555e077c0 <stat_config>, counter=0x555555f289d0, s=0, os=0x7fffffffbf10) at util/stat-display.c:838
#8 0x000055555577c1d8 in print_counter (config=0x555555e077c0 <stat_config>, counter=0x555555f289d0, os=0x7fffffffbf10) at util/stat-display.c:957
#9 0x000055555577dba0 in evlist__print_counters (evlist=0x555555ec3610, config=0x555555e077c0 <stat_config>, _target=0x555555e01c80 <target>, ts=0x0, argc=1, argv=0x7fffffffe450) at util/stat-display.c:1413
#10 0x00005555555fc821 in print_counters (ts=0x0, argc=1, argv=0x7fffffffe450) at builtin-stat.c:1040
#11 0x000055555560091a in cmd_stat (argc=1, argv=0x7fffffffe450) at builtin-stat.c:2665
#12 0x00005555556b1eea in run_builtin (p=0x555555e11f70 <commands+336>, argc=4, argv=0x7fffffffe450) at perf.c:322
#13 0x00005555556b2181 in handle_internal_command (argc=4, argv=0x7fffffffe450) at perf.c:376
#14 0x00005555556b22d7 in run_argv (argcp=0x7fffffffe27c, argv=0x7fffffffe270) at perf.c:420
#15 0x00005555556b26ef in main (argc=4, argv=0x7fffffffe450) at perf.c:550
(gdb)
Fixes: f123b2d ("perf stat: Remove prefix argument in print_metric_headers()")
Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Link: http://lore.kernel.org/lkml/CAP-5=fUOjSM5HajU9TCD6prY39LbX4OQbkEbtKPPGRBPBN=_VQ@mail.gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
buzzcut-s
pushed a commit
to buzzcut-s/android_kernel_nothing_sm7325
that referenced
this issue
Mar 27, 2023
Remove initial SIDs that have never been used or are no longer used by the kernel from its string table, which is also used to generate the SECINITSID_* symbols referenced in code. Update the code to gracefully handle the fact that these can now be NULL. Stop treating it as an error if a policy defines additional initial SIDs unknown to the kernel. Do not load unused initial SID contexts into the sidtab. Fix the incorrect usage of the name from the ocontext in error messages when loading initial SIDs since these are not presently written to the kernel policy and are therefore always NULL. After this change, it is possible to safely reclaim and reuse some of the unused initial SIDs without compatibility issues. Specifically, unused initial SIDs that were being assigned the same context as the unlabeled initial SID in policies can be reclaimed and reused for another purpose, with existing policies still treating them as having the unlabeled context and future policies having the option of mapping them to a more specific context. For example, this could have been used when the infiniband labeling support was introduced to define initial SIDs for the default pkey and endport SIDs similar to the handling of port/netif/node SIDs rather than always using SECINITSID_UNLABELED as the default. The set of safely reclaimable unused initial SIDs across all known policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod (24), policy (25), and scmp_packet (26); these initial SIDs were assigned the same context as unlabeled in all known policies including mls. If only considering non-mls policies (i.e. assuming that mls users always upgrade policy with their kernels), the set of safely reclaimable unused initial SIDs further includes file_labels (6), init (7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23). Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately became a fatal error in commit 24ed7fd ("selinux: use separate table for initial SID lookup") and even before that it could cause problems on a policy reload (collision between the new initial SID and one allocated at runtime) ever since commit 42596ea ("selinux: load the initial SIDs upon every policy load") so we cannot safely start adding new initial SIDs to policies beyond SECINITSID_NUM (27) until such a time as all such kernels do not need to be supported and only those that include this commit are relevant. That is not a big deal since we haven't added a new initial SID since 2004 (v2.6.7) and we have plenty of unused ones we can reclaim if we truly need one. If we want to avoid the wasted storage in initial_sid_to_string[] and/or sidtab->isids[] for the unused initial SIDs, we could introduce an indirection between the kernel initial SID values and the policy initial SID values and just map the policy SID values in the ocontexts to the kernel values during policy_load_isids(). Originally I thought we'd do this by preserving the initial SID names in the kernel policy and creating a mapping at load time like we do for the security classes and permissions but that would require a new kernel policy format version and associated changes to libsepol/checkpolicy and I'm not sure it is justified. Simpler approach is just to create a fixed mapping table in the kernel from the existing fixed policy values to the kernel values. Less flexible but probably sufficient. A separate selinux userspace change was applied in SELinuxProject/selinux@8677ce5 to enable removal of most of the unused initial SID contexts from policies, but there is no dependency between that change and this one. That change permits removing all of the unused initial SID contexts from policy except for the fs and sysctl SID contexts. The initial SID declarations themselves would remain in policy to preserve the values of subsequent ones but the contexts can be dropped. If/when the kernel decides to reuse one of them, future policies can change the name and start assigning a context again without breaking compatibility. Here is how I would envision staging changes to the initial SIDs in a compatible manner after this commit is applied: 1. At any time after this commit is applied, the kernel could choose to reclaim one of the safely reclaimable unused initial SIDs listed above for a new purpose (i.e. replace its NULL entry in the initial_sid_to_string[] table with a new name and start using the newly generated SECINITSID_name symbol in code), and refpolicy could at that time rename its declaration of that initial SID to reflect its new purpose and start assigning it a context going forward. Existing/old policies would map the reclaimed initial SID to the unlabeled context, so that would be the initial default behavior until policies are updated. This doesn't depend on the selinux userspace change; it will work with existing policies and userspace. 2. In 6 months or so we'll have another SELinux userspace release that will include the libsepol/checkpolicy support for omitting unused initial SID contexts. 3. At any time after that release, refpolicy can make that release its minimum build requirement and drop the sid context statements (but not the sid declarations) for all of the unused initial SIDs except for fs and sysctl, which must remain for compatibility on policy reload with old kernels and for compatibility with kernels that were still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this kernel commit; it will work with previous kernels as well. 4. After N years for some value of N, refpolicy decides that it no longer cares about policy reload compatibility for kernels that predate this kernel commit, and refpolicy drops the fs and sysctl SID contexts from policy too (but retains the declarations). 5. After M years for some value of M, the kernel decides that it no longer cares about compatibility with refpolicies that predate step 4 (dropping the fs and sysctl SIDs), and those two SIDs also become safely reclaimable. This step is optional and need not ever occur unless we decide that the need to reclaim those two SIDs outweighs the compatibility cost. 6. After O years for some value of O, refpolicy decides that it no longer cares about policy load (not just reload) compatibility for kernels that predate this kernel commit, and both kernel and refpolicy can then start adding and using new initial SIDs beyond 27. This does not depend on the previous change (step 5) and can occur independent of it. Fixes: SELinuxProject/selinux-kernel#12 Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov> Signed-off-by: Paul Moore <paul@paul-moore.com> Signed-off-by: Juhyung Park <qkrwngud825@gmail.com>
buzzcut-s
pushed a commit
to buzzcut-s/android_kernel_nothing_sm7325
that referenced
this issue
Jun 9, 2023
Remove initial SIDs that have never been used or are no longer used by the kernel from its string table, which is also used to generate the SECINITSID_* symbols referenced in code. Update the code to gracefully handle the fact that these can now be NULL. Stop treating it as an error if a policy defines additional initial SIDs unknown to the kernel. Do not load unused initial SID contexts into the sidtab. Fix the incorrect usage of the name from the ocontext in error messages when loading initial SIDs since these are not presently written to the kernel policy and are therefore always NULL. After this change, it is possible to safely reclaim and reuse some of the unused initial SIDs without compatibility issues. Specifically, unused initial SIDs that were being assigned the same context as the unlabeled initial SID in policies can be reclaimed and reused for another purpose, with existing policies still treating them as having the unlabeled context and future policies having the option of mapping them to a more specific context. For example, this could have been used when the infiniband labeling support was introduced to define initial SIDs for the default pkey and endport SIDs similar to the handling of port/netif/node SIDs rather than always using SECINITSID_UNLABELED as the default. The set of safely reclaimable unused initial SIDs across all known policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod (24), policy (25), and scmp_packet (26); these initial SIDs were assigned the same context as unlabeled in all known policies including mls. If only considering non-mls policies (i.e. assuming that mls users always upgrade policy with their kernels), the set of safely reclaimable unused initial SIDs further includes file_labels (6), init (7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23). Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately became a fatal error in commit 24ed7fd ("selinux: use separate table for initial SID lookup") and even before that it could cause problems on a policy reload (collision between the new initial SID and one allocated at runtime) ever since commit 42596ea ("selinux: load the initial SIDs upon every policy load") so we cannot safely start adding new initial SIDs to policies beyond SECINITSID_NUM (27) until such a time as all such kernels do not need to be supported and only those that include this commit are relevant. That is not a big deal since we haven't added a new initial SID since 2004 (v2.6.7) and we have plenty of unused ones we can reclaim if we truly need one. If we want to avoid the wasted storage in initial_sid_to_string[] and/or sidtab->isids[] for the unused initial SIDs, we could introduce an indirection between the kernel initial SID values and the policy initial SID values and just map the policy SID values in the ocontexts to the kernel values during policy_load_isids(). Originally I thought we'd do this by preserving the initial SID names in the kernel policy and creating a mapping at load time like we do for the security classes and permissions but that would require a new kernel policy format version and associated changes to libsepol/checkpolicy and I'm not sure it is justified. Simpler approach is just to create a fixed mapping table in the kernel from the existing fixed policy values to the kernel values. Less flexible but probably sufficient. A separate selinux userspace change was applied in SELinuxProject/selinux@8677ce5 to enable removal of most of the unused initial SID contexts from policies, but there is no dependency between that change and this one. That change permits removing all of the unused initial SID contexts from policy except for the fs and sysctl SID contexts. The initial SID declarations themselves would remain in policy to preserve the values of subsequent ones but the contexts can be dropped. If/when the kernel decides to reuse one of them, future policies can change the name and start assigning a context again without breaking compatibility. Here is how I would envision staging changes to the initial SIDs in a compatible manner after this commit is applied: 1. At any time after this commit is applied, the kernel could choose to reclaim one of the safely reclaimable unused initial SIDs listed above for a new purpose (i.e. replace its NULL entry in the initial_sid_to_string[] table with a new name and start using the newly generated SECINITSID_name symbol in code), and refpolicy could at that time rename its declaration of that initial SID to reflect its new purpose and start assigning it a context going forward. Existing/old policies would map the reclaimed initial SID to the unlabeled context, so that would be the initial default behavior until policies are updated. This doesn't depend on the selinux userspace change; it will work with existing policies and userspace. 2. In 6 months or so we'll have another SELinux userspace release that will include the libsepol/checkpolicy support for omitting unused initial SID contexts. 3. At any time after that release, refpolicy can make that release its minimum build requirement and drop the sid context statements (but not the sid declarations) for all of the unused initial SIDs except for fs and sysctl, which must remain for compatibility on policy reload with old kernels and for compatibility with kernels that were still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this kernel commit; it will work with previous kernels as well. 4. After N years for some value of N, refpolicy decides that it no longer cares about policy reload compatibility for kernels that predate this kernel commit, and refpolicy drops the fs and sysctl SID contexts from policy too (but retains the declarations). 5. After M years for some value of M, the kernel decides that it no longer cares about compatibility with refpolicies that predate step 4 (dropping the fs and sysctl SIDs), and those two SIDs also become safely reclaimable. This step is optional and need not ever occur unless we decide that the need to reclaim those two SIDs outweighs the compatibility cost. 6. After O years for some value of O, refpolicy decides that it no longer cares about policy load (not just reload) compatibility for kernels that predate this kernel commit, and both kernel and refpolicy can then start adding and using new initial SIDs beyond 27. This does not depend on the previous change (step 5) and can occur independent of it. Fixes: SELinuxProject/selinux-kernel#12 Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov> Signed-off-by: Paul Moore <paul@paul-moore.com> Signed-off-by: Juhyung Park <qkrwngud825@gmail.com>
meydiwahendra
pushed a commit
to meydiwahendra/android_kernel_xiaomi_whyred
that referenced
this issue
Sep 9, 2023
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fdae669 ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Reinazhard <reinazhard@gmail.com>
Signed-off-by: meydiwahendra <meydiwahendra@gmail.com>
pcmoore
pushed a commit
that referenced
this issue
Sep 11, 2023
Currently, arch_stack_walk() can only get the full stack information including NMI. This is because the implementation of arch_stack_walk() is forced to ignore the information passed by the regs parameter and use the current stack information instead. For some detection systems like KFENCE, only partial stack information is needed. In particular, the stack frame where the interrupt occurred. To support KFENCE, this patch modifies the implementation of the arch_stack_walk() function so that if this function is called with the regs argument passed, it retains all the stack information in regs and uses it to provide accurate information. Before this patch: [ 1.531195 ] ================================================================== [ 1.531442 ] BUG: KFENCE: out-of-bounds read in stack_trace_save_regs+0x48/0x6c [ 1.531442 ] [ 1.531900 ] Out-of-bounds read at 0xffff800012267fff (1B left of kfence-#12): [ 1.532046 ] stack_trace_save_regs+0x48/0x6c [ 1.532169 ] kfence_report_error+0xa4/0x528 [ 1.532276 ] kfence_handle_page_fault+0x124/0x270 [ 1.532388 ] no_context+0x50/0x94 [ 1.532453 ] do_page_fault+0x1a8/0x36c [ 1.532524 ] tlb_do_page_fault_0+0x118/0x1b4 [ 1.532623 ] test_out_of_bounds_read+0xa0/0x1d8 [ 1.532745 ] kunit_generic_run_threadfn_adapter+0x1c/0x28 [ 1.532854 ] kthread+0x124/0x130 [ 1.532922 ] ret_from_kernel_thread+0xc/0xa4 <snip> After this patch: [ 1.320220 ] ================================================================== [ 1.320401 ] BUG: KFENCE: out-of-bounds read in test_out_of_bounds_read+0xa8/0x1d8 [ 1.320401 ] [ 1.320898 ] Out-of-bounds read at 0xffff800012257fff (1B left of kfence-#10): [ 1.321134 ] test_out_of_bounds_read+0xa8/0x1d8 [ 1.321264 ] kunit_generic_run_threadfn_adapter+0x1c/0x28 [ 1.321392 ] kthread+0x124/0x130 [ 1.321459 ] ret_from_kernel_thread+0xc/0xa4 <snip> Suggested-by: Jinyang He <hejinyang@loongson.cn> Signed-off-by: Enze Li <lienze@kylinos.cn> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
pcmoore
pushed a commit
that referenced
this issue
Nov 13, 2023
Fix kernel crash in AP bus code caused by very early invocation of the config change callback function via SCLP. After a fresh IML of the machine the crypto cards are still offline and will get switched online only with activation of any LPAR which has the card in it's configuration. A crypto card coming online is reported to the LPAR via SCLP and the AP bus offers a callback function to get this kind of information. However, it may happen that the callback is invoked before the AP bus init function is complete. As the callback triggers a synchronous AP bus scan, the scan may already run but some internal states are not initialized by the AP bus init function resulting in a crash like this: [ 11.635859] Unable to handle kernel pointer dereference in virtual kernel address space [ 11.635861] Failing address: 0000000000000000 TEID: 0000000000000887 [ 11.635862] Fault in home space mode while using kernel ASCE. [ 11.635864] AS:00000000894c4007 R3:00000001fece8007 S:00000001fece7800 P:000000000000013d [ 11.635879] Oops: 0004 ilc:1 [#1] SMP [ 11.635882] Modules linked in: [ 11.635884] CPU: 5 PID: 42 Comm: kworker/5:0 Not tainted 6.6.0-rc3-00003-g4dbf7cdc6b42 #12 [ 11.635886] Hardware name: IBM 3931 A01 751 (LPAR) [ 11.635887] Workqueue: events_long ap_scan_bus [ 11.635891] Krnl PSW : 0704c00180000000 0000000000000000 (0x0) [ 11.635895] R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:0 PM:0 RI:0 EA:3 [ 11.635897] Krnl GPRS: 0000000001000a00 0000000000000000 0000000000000006 0000000089591940 [ 11.635899] 0000000080000000 0000000000000a00 0000000000000000 0000000000000000 [ 11.635901] 0000000081870c00 0000000089591000 000000008834e4e2 0000000002625a00 [ 11.635903] 0000000081734200 0000038000913c18 000000008834c6d6 0000038000913ac8 [ 11.635906] Krnl Code:>0000000000000000: 0000 illegal [ 11.635906] 0000000000000002: 0000 illegal [ 11.635906] 0000000000000004: 0000 illegal [ 11.635906] 0000000000000006: 0000 illegal [ 11.635906] 0000000000000008: 0000 illegal [ 11.635906] 000000000000000a: 0000 illegal [ 11.635906] 000000000000000c: 0000 illegal [ 11.635906] 000000000000000e: 0000 illegal [ 11.635915] Call Trace: [ 11.635916] [<0000000000000000>] 0x0 [ 11.635918] [<000000008834e4e2>] ap_queue_init_state+0x82/0xb8 [ 11.635921] [<000000008834ba1c>] ap_scan_domains+0x6fc/0x740 [ 11.635923] [<000000008834c092>] ap_scan_adapter+0x632/0x8b0 [ 11.635925] [<000000008834c3e4>] ap_scan_bus+0xd4/0x288 [ 11.635927] [<00000000879a33ba>] process_one_work+0x19a/0x410 [ 11.635930] Discipline DIAG cannot be used without z/VM [ 11.635930] [<00000000879a3a2c>] worker_thread+0x3fc/0x560 [ 11.635933] [<00000000879aea60>] kthread+0x120/0x128 [ 11.635936] [<000000008792afa4>] __ret_from_fork+0x3c/0x58 [ 11.635938] [<00000000885ebe62>] ret_from_fork+0xa/0x30 [ 11.635942] Last Breaking-Event-Address: [ 11.635942] [<000000008834c6d4>] ap_wait+0xcc/0x148 This patch improves the ap_bus_force_rescan() function which is invoked by the config change callback by checking if a first initial AP bus scan has been done. If not, the force rescan request is simple ignored. Anyhow it does not make sense to trigger AP bus re-scans even before the very first bus scan is complete. Cc: stable@vger.kernel.org Reviewed-by: Holger Dengler <dengler@linux.ibm.com> Signed-off-by: Harald Freudenberger <freude@linux.ibm.com> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
LeCmnGend
added a commit
to LeCmnGend/kernel_xiaomi_raphael
that referenced
this issue
Dec 15, 2023
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fd ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Juhyung Park <qkrwngud825@gmail.com>
LeCmnGend
added a commit
to LeCmnGend/kernel_xiaomi_violet
that referenced
this issue
Jan 8, 2024
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fd ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Juhyung Park <qkrwngud825@gmail.com>
LeCmnGend
added a commit
to LeCmnGend/kernel_xiaomi_violet
that referenced
this issue
Jan 8, 2024
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fd ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Juhyung Park <qkrwngud825@gmail.com>
LeCmnGend
added a commit
to LeCmnGend/kernel_xiaomi_violet
that referenced
this issue
Jan 8, 2024
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fd ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Juhyung Park <qkrwngud825@gmail.com>
LeCmnGend
added a commit
to LeCmnGend/kernel_xiaomi_violet
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this issue
Jan 8, 2024
Remove initial SIDs that have never been used or are no longer used by
the kernel from its string table, which is also used to generate the
SECINITSID_* symbols referenced in code. Update the code to
gracefully handle the fact that these can now be NULL. Stop treating
it as an error if a policy defines additional initial SIDs unknown to
the kernel. Do not load unused initial SID contexts into the sidtab.
Fix the incorrect usage of the name from the ocontext in error
messages when loading initial SIDs since these are not presently
written to the kernel policy and are therefore always NULL.
After this change, it is possible to safely reclaim and reuse some of
the unused initial SIDs without compatibility issues. Specifically,
unused initial SIDs that were being assigned the same context as the
unlabeled initial SID in policies can be reclaimed and reused for
another purpose, with existing policies still treating them as having
the unlabeled context and future policies having the option of mapping
them to a more specific context. For example, this could have been
used when the infiniband labeling support was introduced to define
initial SIDs for the default pkey and endport SIDs similar to the
handling of port/netif/node SIDs rather than always using
SECINITSID_UNLABELED as the default.
The set of safely reclaimable unused initial SIDs across all known
policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod
(24), policy (25), and scmp_packet (26); these initial SIDs were
assigned the same context as unlabeled in all known policies including
mls. If only considering non-mls policies (i.e. assuming that mls
users always upgrade policy with their kernels), the set of safely
reclaimable unused initial SIDs further includes file_labels (6), init
(7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23).
Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately
became a fatal error in commit 24ed7fd ("selinux: use separate
table for initial SID lookup") and even before that it could cause
problems on a policy reload (collision between the new initial SID and
one allocated at runtime) ever since commit 42596ea ("selinux:
load the initial SIDs upon every policy load") so we cannot safely
start adding new initial SIDs to policies beyond SECINITSID_NUM (27)
until such a time as all such kernels do not need to be supported and
only those that include this commit are relevant. That is not a big
deal since we haven't added a new initial SID since 2004 (v2.6.7) and
we have plenty of unused ones we can reclaim if we truly need one.
If we want to avoid the wasted storage in initial_sid_to_string[]
and/or sidtab->isids[] for the unused initial SIDs, we could introduce
an indirection between the kernel initial SID values and the policy
initial SID values and just map the policy SID values in the ocontexts
to the kernel values during policy_load_isids(). Originally I thought
we'd do this by preserving the initial SID names in the kernel policy
and creating a mapping at load time like we do for the security
classes and permissions but that would require a new kernel policy
format version and associated changes to libsepol/checkpolicy and I'm
not sure it is justified. Simpler approach is just to create a fixed
mapping table in the kernel from the existing fixed policy values to
the kernel values. Less flexible but probably sufficient.
A separate selinux userspace change was applied in
SELinuxProject/selinux@8677ce5
to enable removal of most of the unused initial SID contexts from
policies, but there is no dependency between that change and this one.
That change permits removing all of the unused initial SID contexts
from policy except for the fs and sysctl SID contexts. The initial
SID declarations themselves would remain in policy to preserve the
values of subsequent ones but the contexts can be dropped. If/when
the kernel decides to reuse one of them, future policies can change
the name and start assigning a context again without breaking
compatibility.
Here is how I would envision staging changes to the initial SIDs in a
compatible manner after this commit is applied:
1. At any time after this commit is applied, the kernel could choose
to reclaim one of the safely reclaimable unused initial SIDs listed
above for a new purpose (i.e. replace its NULL entry in the
initial_sid_to_string[] table with a new name and start using the
newly generated SECINITSID_name symbol in code), and refpolicy could
at that time rename its declaration of that initial SID to reflect its
new purpose and start assigning it a context going
forward. Existing/old policies would map the reclaimed initial SID to
the unlabeled context, so that would be the initial default behavior
until policies are updated. This doesn't depend on the selinux
userspace change; it will work with existing policies and userspace.
2. In 6 months or so we'll have another SELinux userspace release that
will include the libsepol/checkpolicy support for omitting unused
initial SID contexts.
3. At any time after that release, refpolicy can make that release its
minimum build requirement and drop the sid context statements (but not
the sid declarations) for all of the unused initial SIDs except for
fs and sysctl, which must remain for compatibility on policy
reload with old kernels and for compatibility with kernels that were
still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this
kernel commit; it will work with previous kernels as well.
4. After N years for some value of N, refpolicy decides that it no
longer cares about policy reload compatibility for kernels that
predate this kernel commit, and refpolicy drops the fs and sysctl
SID contexts from policy too (but retains the declarations).
5. After M years for some value of M, the kernel decides that it no
longer cares about compatibility with refpolicies that predate step 4
(dropping the fs and sysctl SIDs), and those two SIDs also become
safely reclaimable. This step is optional and need not ever occur unless
we decide that the need to reclaim those two SIDs outweighs the
compatibility cost.
6. After O years for some value of O, refpolicy decides that it no
longer cares about policy load (not just reload) compatibility for
kernels that predate this kernel commit, and both kernel and refpolicy
can then start adding and using new initial SIDs beyond 27. This does
not depend on the previous change (step 5) and can occur independent
of it.
Fixes: SELinuxProject/selinux-kernel#12
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Juhyung Park <qkrwngud825@gmail.com>
pcmoore
pushed a commit
that referenced
this issue
Jan 22, 2024
nvif_vmm_put gets called if addr is set, but if the allocation fails we don't need to call put, otherwise we get a warning like [523232.435671] ------------[ cut here ]------------ [523232.435674] WARNING: CPU: 8 PID: 1505697 at drivers/gpu/drm/nouveau/nvif/vmm.c:68 nvif_vmm_put+0x72/0x80 [nouveau] [523232.435795] Modules linked in: uinput rfcomm snd_seq_dummy snd_hrtimer nf_conntrack_netbios_ns nf_conntrack_broadcast nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip_set nf_tables nfnetlink qrtr bnep sunrpc binfmt_misc intel_rapl_msr intel_rapl_common intel_uncore_frequency intel_uncore_frequency_common isst_if_common iwlmvm nfit libnvdimm vfat fat x86_pkg_temp_thermal intel_powerclamp mac80211 snd_soc_avs snd_soc_hda_codec coretemp snd_hda_ext_core snd_soc_core snd_hda_codec_realtek kvm_intel snd_hda_codec_hdmi snd_compress snd_hda_codec_generic ac97_bus snd_pcm_dmaengine snd_hda_intel libarc4 snd_intel_dspcfg snd_intel_sdw_acpi snd_hda_codec kvm iwlwifi snd_hda_core btusb snd_hwdep btrtl snd_seq btintel irqbypass btbcm rapl snd_seq_device eeepc_wmi btmtk intel_cstate iTCO_wdt cfg80211 snd_pcm asus_wmi bluetooth intel_pmc_bxt iTCO_vendor_support snd_timer ledtrig_audio pktcdvd snd mei_me [523232.435828] sparse_keymap intel_uncore i2c_i801 platform_profile wmi_bmof mei pcspkr ioatdma soundcore i2c_smbus rfkill idma64 dca joydev acpi_tad loop zram nouveau drm_ttm_helper ttm video drm_exec drm_gpuvm gpu_sched crct10dif_pclmul i2c_algo_bit nvme crc32_pclmul crc32c_intel drm_display_helper polyval_clmulni nvme_core polyval_generic e1000e mxm_wmi cec ghash_clmulni_intel r8169 sha512_ssse3 nvme_common wmi pinctrl_sunrisepoint uas usb_storage ip6_tables ip_tables fuse [523232.435849] CPU: 8 PID: 1505697 Comm: gnome-shell Tainted: G W 6.6.0-rc7-nvk-uapi+ #12 [523232.435851] Hardware name: System manufacturer System Product Name/ROG STRIX X299-E GAMING II, BIOS 1301 09/24/2021 [523232.435852] RIP: 0010:nvif_vmm_put+0x72/0x80 [nouveau] [523232.435934] Code: 00 00 48 89 e2 be 02 00 00 00 48 c7 04 24 00 00 00 00 48 89 44 24 08 e8 fc bf ff ff 85 c0 75 0a 48 c7 43 08 00 00 00 00 eb b3 <0f> 0b eb f2 e8 f5 c9 b2 e6 0f 1f 44 00 00 90 90 90 90 90 90 90 90 [523232.435936] RSP: 0018:ffffc900077ffbd8 EFLAGS: 00010282 [523232.435937] RAX: 00000000fffffffe RBX: ffffc900077ffc00 RCX: 0000000000000010 [523232.435938] RDX: 0000000000000010 RSI: ffffc900077ffb38 RDI: ffffc900077ffbd8 [523232.435940] RBP: ffff888e1c4f2140 R08: 0000000000000000 R09: 0000000000000000 [523232.435940] R10: 0000000000000000 R11: 0000000000000000 R12: ffff888503811800 [523232.435941] R13: ffffc900077ffca0 R14: ffff888e1c4f2140 R15: ffff88810317e1e0 [523232.435942] FS: 00007f933a769640(0000) GS:ffff88905fa00000(0000) knlGS:0000000000000000 [523232.435943] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [523232.435944] CR2: 00007f930bef7000 CR3: 00000005d0322001 CR4: 00000000003706e0 [523232.435945] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [523232.435946] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [523232.435964] Call Trace: [523232.435965] <TASK> [523232.435966] ? nvif_vmm_put+0x72/0x80 [nouveau] [523232.436051] ? __warn+0x81/0x130 [523232.436055] ? nvif_vmm_put+0x72/0x80 [nouveau] [523232.436138] ? report_bug+0x171/0x1a0 [523232.436142] ? handle_bug+0x3c/0x80 [523232.436144] ? exc_invalid_op+0x17/0x70 [523232.436145] ? asm_exc_invalid_op+0x1a/0x20 [523232.436149] ? nvif_vmm_put+0x72/0x80 [nouveau] [523232.436230] ? nvif_vmm_put+0x64/0x80 [nouveau] [523232.436342] nouveau_vma_del+0x80/0xd0 [nouveau] [523232.436506] nouveau_vma_new+0x1a0/0x210 [nouveau] [523232.436671] nouveau_gem_object_open+0x1d0/0x1f0 [nouveau] [523232.436835] drm_gem_handle_create_tail+0xd1/0x180 [523232.436840] drm_prime_fd_to_handle_ioctl+0x12e/0x200 [523232.436844] ? __pfx_drm_prime_fd_to_handle_ioctl+0x10/0x10 [523232.436847] drm_ioctl_kernel+0xd3/0x180 [523232.436849] drm_ioctl+0x26d/0x4b0 [523232.436851] ? __pfx_drm_prime_fd_to_handle_ioctl+0x10/0x10 [523232.436855] nouveau_drm_ioctl+0x5a/0xb0 [nouveau] [523232.437032] __x64_sys_ioctl+0x94/0xd0 [523232.437036] do_syscall_64+0x5d/0x90 [523232.437040] ? syscall_exit_to_user_mode+0x2b/0x40 [523232.437044] ? do_syscall_64+0x6c/0x90 [523232.437046] entry_SYSCALL_64_after_hwframe+0x6e/0xd8 Reported-by: Faith Ekstrand <faith.ekstrand@collabora.com> Cc: stable@vger.kernel.org Signed-off-by: Dave Airlie <airlied@redhat.com> Link: https://patchwork.freedesktop.org/patch/msgid/20240117213852.295565-1-airlied@gmail.com
stephensmalley
pushed a commit
to stephensmalley/selinux-kernel
that referenced
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May 2, 2024
vhost_worker will call tun call backs to receive packets. If too many illegal packets arrives, tun_do_read will keep dumping packet contents. When console is enabled, it will costs much more cpu time to dump packet and soft lockup will be detected. net_ratelimit mechanism can be used to limit the dumping rate. PID: 33036 TASK: ffff949da6f20000 CPU: 23 COMMAND: "vhost-32980" #0 [fffffe00003fce50] crash_nmi_callback at ffffffff89249253 SELinuxProject#1 [fffffe00003fce58] nmi_handle at ffffffff89225fa3 SELinuxProject#2 [fffffe00003fceb0] default_do_nmi at ffffffff8922642e SELinuxProject#3 [fffffe00003fced0] do_nmi at ffffffff8922660d SELinuxProject#4 [fffffe00003fcef0] end_repeat_nmi at ffffffff89c01663 [exception RIP: io_serial_in+20] RIP: ffffffff89792594 RSP: ffffa655314979e8 RFLAGS: 00000002 RAX: ffffffff89792500 RBX: ffffffff8af428a0 RCX: 0000000000000000 RDX: 00000000000003fd RSI: 0000000000000005 RDI: ffffffff8af428a0 RBP: 0000000000002710 R8: 0000000000000004 R9: 000000000000000f R10: 0000000000000000 R11: ffffffff8acbf64f R12: 0000000000000020 R13: ffffffff8acbf698 R14: 0000000000000058 R15: 0000000000000000 ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 SELinuxProject#5 [ffffa655314979e8] io_serial_in at ffffffff89792594 SELinuxProject#6 [ffffa655314979e8] wait_for_xmitr at ffffffff89793470 SELinuxProject#7 [ffffa65531497a08] serial8250_console_putchar at ffffffff897934f6 SELinuxProject#8 [ffffa65531497a20] uart_console_write at ffffffff8978b605 SELinuxProject#9 [ffffa65531497a48] serial8250_console_write at ffffffff89796558 SELinuxProject#10 [ffffa65531497ac8] console_unlock at ffffffff89316124 SELinuxProject#11 [ffffa65531497b10] vprintk_emit at ffffffff89317c07 SELinuxProject#12 [ffffa65531497b68] printk at ffffffff89318306 SELinuxProject#13 [ffffa65531497bc8] print_hex_dump at ffffffff89650765 SELinuxProject#14 [ffffa65531497ca8] tun_do_read at ffffffffc0b06c27 [tun] SELinuxProject#15 [ffffa65531497d38] tun_recvmsg at ffffffffc0b06e34 [tun] SELinuxProject#16 [ffffa65531497d68] handle_rx at ffffffffc0c5d682 [vhost_net] SELinuxProject#17 [ffffa65531497ed0] vhost_worker at ffffffffc0c644dc [vhost] SELinuxProject#18 [ffffa65531497f10] kthread at ffffffff892d2e72 SELinuxProject#19 [ffffa65531497f50] ret_from_fork at ffffffff89c0022f Fixes: ef3db4a ("tun: avoid BUG, dump packet on GSO errors") Signed-off-by: Lei Chen <lei.chen@smartx.com> Reviewed-by: Willem de Bruijn <willemb@google.com> Acked-by: Jason Wang <jasowang@redhat.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Link: https://lore.kernel.org/r/20240415020247.2207781-1-lei.chen@smartx.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
stephensmalley
pushed a commit
to stephensmalley/selinux-kernel
that referenced
this issue
May 15, 2024
Commit 1548036 ("nfs: make the rpc_stat per net namespace") added functionality to specify rpc_stats function but missed adding it to the TCP TLS functionality. As the result, mounting with xprtsec=tls lead to the following kernel oops. [ 128.984192] Unable to handle kernel NULL pointer dereference at virtual address 000000000000001c [ 128.985058] Mem abort info: [ 128.985372] ESR = 0x0000000096000004 [ 128.985709] EC = 0x25: DABT (current EL), IL = 32 bits [ 128.986176] SET = 0, FnV = 0 [ 128.986521] EA = 0, S1PTW = 0 [ 128.986804] FSC = 0x04: level 0 translation fault [ 128.987229] Data abort info: [ 128.987597] ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000 [ 128.988169] CM = 0, WnR = 0, TnD = 0, TagAccess = 0 [ 128.988811] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 [ 128.989302] user pgtable: 4k pages, 48-bit VAs, pgdp=0000000106c84000 [ 128.990048] [000000000000001c] pgd=0000000000000000, p4d=0000000000000000 [ 128.990736] Internal error: Oops: 0000000096000004 [SELinuxProject#1] SMP [ 128.991168] Modules linked in: nfs_layout_nfsv41_files rpcsec_gss_krb5 auth_rpcgss nfsv4 dns_resolver nfs lockd grace netfs uinput dm_mod nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 rfkill ip_set nf_tables nfnetlink qrtr vsock_loopback vmw_vsock_virtio_transport_common vmw_vsock_vmci_transport vsock sunrpc vfat fat uvcvideo videobuf2_vmalloc videobuf2_memops uvc videobuf2_v4l2 videodev videobuf2_common mc vmw_vmci xfs libcrc32c e1000e crct10dif_ce ghash_ce sha2_ce vmwgfx nvme sha256_arm64 nvme_core sr_mod cdrom sha1_ce drm_ttm_helper ttm drm_kms_helper drm sg fuse [ 128.996466] CPU: 0 PID: 179 Comm: kworker/u4:26 Kdump: loaded Not tainted 6.8.0-rc6+ SELinuxProject#12 [ 128.997226] Hardware name: VMware, Inc. VMware20,1/VBSA, BIOS VMW201.00V.21805430.BA64.2305221830 05/22/2023 [ 128.998084] Workqueue: xprtiod xs_tcp_tls_setup_socket [sunrpc] [ 128.998701] pstate: 81400005 (Nzcv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--) [ 128.999384] pc : call_start+0x74/0x138 [sunrpc] [ 128.999809] lr : __rpc_execute+0xb8/0x3e0 [sunrpc] [ 129.000244] sp : ffff8000832b3a00 [ 129.000508] x29: ffff8000832b3a00 x28: ffff800081ac79c0 x27: ffff800081ac7000 [ 129.001111] x26: 0000000004248060 x25: 0000000000000000 x24: ffff800081596008 [ 129.001757] x23: ffff80007b087240 x22: ffff00009a509d30 x21: 0000000000000000 [ 129.002345] x20: ffff000090075600 x19: ffff00009a509d00 x18: ffffffffffffffff [ 129.002912] x17: 733d4d4554535953 x16: 42555300312d746e x15: ffff8000832b3a88 [ 129.003464] x14: ffffffffffffffff x13: ffff8000832b3a7d x12: 0000000000000008 [ 129.004021] x11: 0101010101010101 x10: ffff8000150cb560 x9 : ffff80007b087c00 [ 129.004577] x8 : ffff00009a509de0 x7 : 0000000000000000 x6 : 00000000be8c4ee3 [ 129.005026] x5 : 0000000000000000 x4 : 0000000000000000 x3 : ffff000094d56680 [ 129.005425] x2 : ffff80007b0637f8 x1 : ffff000090075600 x0 : ffff00009a509d00 [ 129.005824] Call trace: [ 129.005967] call_start+0x74/0x138 [sunrpc] [ 129.006233] __rpc_execute+0xb8/0x3e0 [sunrpc] [ 129.006506] rpc_execute+0x160/0x1d8 [sunrpc] [ 129.006778] rpc_run_task+0x148/0x1f8 [sunrpc] [ 129.007204] tls_probe+0x80/0xd0 [sunrpc] [ 129.007460] rpc_ping+0x28/0x80 [sunrpc] [ 129.007715] rpc_create_xprt+0x134/0x1a0 [sunrpc] [ 129.007999] rpc_create+0x128/0x2a0 [sunrpc] [ 129.008264] xs_tcp_tls_setup_socket+0xdc/0x508 [sunrpc] [ 129.008583] process_one_work+0x174/0x3c8 [ 129.008813] worker_thread+0x2c8/0x3e0 [ 129.009033] kthread+0x100/0x110 [ 129.009225] ret_from_fork+0x10/0x20 [ 129.009432] Code: f0ffffc2 911fe042 aa1403e1 aa1303e0 (b9401c83) Fixes: 1548036 ("nfs: make the rpc_stat per net namespace") Signed-off-by: Olga Kornievskaia <kolga@netapp.com> Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
stephensmalley
pushed a commit
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that referenced
this issue
May 15, 2024
syzkaller reported a warning [0] triggered while destroying immature netns. rpc_proc_register() was called in init_nfs_fs(), but its error has been ignored since at least the initial commit 1da177e ("Linux-2.6.12-rc2"). Recently, commit d47151b ("nfs: expose /proc/net/sunrpc/nfs in net namespaces") converted the procfs to per-netns and made the problem more visible. Even when rpc_proc_register() fails, nfs_net_init() could succeed, and thus nfs_net_exit() will be called while destroying the netns. Then, remove_proc_entry() will be called for non-existing proc directory and trigger the warning below. Let's handle the error of rpc_proc_register() properly in nfs_net_init(). [0]: name 'nfs' WARNING: CPU: 1 PID: 1710 at fs/proc/generic.c:711 remove_proc_entry+0x1bb/0x2d0 fs/proc/generic.c:711 Modules linked in: CPU: 1 PID: 1710 Comm: syz-executor.2 Not tainted 6.8.0-12822-gcd51db110a7e SELinuxProject#12 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 RIP: 0010:remove_proc_entry+0x1bb/0x2d0 fs/proc/generic.c:711 Code: 41 5d 41 5e c3 e8 85 09 b5 ff 48 c7 c7 88 58 64 86 e8 09 0e 71 02 e8 74 09 b5 ff 4c 89 e6 48 c7 c7 de 1b 80 84 e8 c5 ad 97 ff <0f> 0b eb b1 e8 5c 09 b5 ff 48 c7 c7 88 58 64 86 e8 e0 0d 71 02 eb RSP: 0018:ffffc9000c6d7ce0 EFLAGS: 00010286 RAX: 0000000000000000 RBX: ffff8880422b8b00 RCX: ffffffff8110503c RDX: ffff888030652f00 RSI: ffffffff81105045 RDI: 0000000000000001 RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000001 R11: ffffffff81bb62cb R12: ffffffff84807ffc R13: ffff88804ad6fcc0 R14: ffffffff84807ffc R15: ffffffff85741ff8 FS: 00007f30cfba8640(0000) GS:ffff88807dd00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ff51afe8000 CR3: 000000005a60a005 CR4: 0000000000770ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 PKRU: 55555554 Call Trace: <TASK> rpc_proc_unregister+0x64/0x70 net/sunrpc/stats.c:310 nfs_net_exit+0x1c/0x30 fs/nfs/inode.c:2438 ops_exit_list+0x62/0xb0 net/core/net_namespace.c:170 setup_net+0x46c/0x660 net/core/net_namespace.c:372 copy_net_ns+0x244/0x590 net/core/net_namespace.c:505 create_new_namespaces+0x2ed/0x770 kernel/nsproxy.c:110 unshare_nsproxy_namespaces+0xae/0x160 kernel/nsproxy.c:228 ksys_unshare+0x342/0x760 kernel/fork.c:3322 __do_sys_unshare kernel/fork.c:3393 [inline] __se_sys_unshare kernel/fork.c:3391 [inline] __x64_sys_unshare+0x1f/0x30 kernel/fork.c:3391 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0x4f/0x110 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x46/0x4e RIP: 0033:0x7f30d0febe5d Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 73 9f 1b 00 f7 d8 64 89 01 48 RSP: 002b:00007f30cfba7cc8 EFLAGS: 00000246 ORIG_RAX: 0000000000000110 RAX: ffffffffffffffda RBX: 00000000004bbf80 RCX: 00007f30d0febe5d RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000006c020600 RBP: 00000000004bbf80 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002 R13: 000000000000000b R14: 00007f30d104c530 R15: 0000000000000000 </TASK> Fixes: 1da177e ("Linux-2.6.12-rc2") Reported-by: syzkaller <syzkaller@googlegroups.com> Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
stephensmalley
pushed a commit
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that referenced
this issue
May 15, 2024
With BPF_PROBE_MEM, BPF allows de-referencing an untrusted pointer. To
thwart invalid memory accesses, the JITs add an exception table entry
for all such accesses. But in case the src_reg + offset is a userspace
address, the BPF program might read that memory if the user has
mapped it.
Make the verifier add guard instructions around such memory accesses and
skip the load if the address falls into the userspace region.
The JITs need to implement bpf_arch_uaddress_limit() to define where
the userspace addresses end for that architecture or TASK_SIZE is taken
as default.
The implementation is as follows:
REG_AX = SRC_REG
if(offset)
REG_AX += offset;
REG_AX >>= 32;
if (REG_AX <= (uaddress_limit >> 32))
DST_REG = 0;
else
DST_REG = *(size *)(SRC_REG + offset);
Comparing just the upper 32 bits of the load address with the upper
32 bits of uaddress_limit implies that the values are being aligned down
to a 4GB boundary before comparison.
The above means that all loads with address <= uaddress_limit + 4GB are
skipped. This is acceptable because there is a large hole (much larger
than 4GB) between userspace and kernel space memory, therefore a
correctly functioning BPF program should not access this 4GB memory
above the userspace.
Let's analyze what this patch does to the following fentry program
dereferencing an untrusted pointer:
SEC("fentry/tcp_v4_connect")
int BPF_PROG(fentry_tcp_v4_connect, struct sock *sk)
{
*(volatile long *)sk;
return 0;
}
BPF Program before | BPF Program after
------------------ | -----------------
0: (79) r1 = *(u64 *)(r1 +0) 0: (79) r1 = *(u64 *)(r1 +0)
-----------------------------------------------------------------------
1: (79) r1 = *(u64 *)(r1 +0) --\ 1: (bf) r11 = r1
----------------------------\ \ 2: (77) r11 >>= 32
2: (b7) r0 = 0 \ \ 3: (b5) if r11 <= 0x8000 goto pc+2
3: (95) exit \ \-> 4: (79) r1 = *(u64 *)(r1 +0)
\ 5: (05) goto pc+1
\ 6: (b7) r1 = 0
\--------------------------------------
7: (b7) r0 = 0
8: (95) exit
As you can see from above, in the best case (off=0), 5 extra instructions
are emitted.
Now, we analyze the same program after it has gone through the JITs of
ARM64 and RISC-V architectures. We follow the single load instruction
that has the untrusted pointer and see what instrumentation has been
added around it.
x86-64 JIT
==========
JIT's Instrumentation
(upstream)
---------------------
0: nopl 0x0(%rax,%rax,1)
5: xchg %ax,%ax
7: push %rbp
8: mov %rsp,%rbp
b: mov 0x0(%rdi),%rdi
---------------------------------
f: movabs $0x800000000000,%r11
19: cmp %r11,%rdi
1c: jb 0x000000000000002a
1e: mov %rdi,%r11
21: add $0x0,%r11
28: jae 0x000000000000002e
2a: xor %edi,%edi
2c: jmp 0x0000000000000032
2e: mov 0x0(%rdi),%rdi
---------------------------------
32: xor %eax,%eax
34: leave
35: ret
The x86-64 JIT already emits some instructions to protect against user
memory access. This patch doesn't make any changes for the x86-64 JIT.
ARM64 JIT
=========
No Intrumentation Verifier's Instrumentation
(upstream) (This patch)
----------------- --------------------------
0: add x9, x30, #0x0 0: add x9, x30, #0x0
4: nop 4: nop
8: paciasp 8: paciasp
c: stp x29, x30, [sp, #-16]! c: stp x29, x30, [sp, #-16]!
10: mov x29, sp 10: mov x29, sp
14: stp x19, x20, [sp, #-16]! 14: stp x19, x20, [sp, #-16]!
18: stp x21, x22, [sp, #-16]! 18: stp x21, x22, [sp, #-16]!
1c: stp x25, x26, [sp, #-16]! 1c: stp x25, x26, [sp, #-16]!
20: stp x27, x28, [sp, #-16]! 20: stp x27, x28, [sp, #-16]!
24: mov x25, sp 24: mov x25, sp
28: mov x26, #0x0 28: mov x26, #0x0
2c: sub x27, x25, #0x0 2c: sub x27, x25, #0x0
30: sub sp, sp, #0x0 30: sub sp, sp, #0x0
34: ldr x0, [x0] 34: ldr x0, [x0]
--------------------------------------------------------------------------------
38: ldr x0, [x0] ----------\ 38: add x9, x0, #0x0
-----------------------------------\\ 3c: lsr x9, x9, SELinuxProject#32
3c: mov x7, #0x0 \\ 40: cmp x9, #0x10, lsl SELinuxProject#12
40: mov sp, sp \\ 44: b.ls 0x0000000000000050
44: ldp x27, x28, [sp], SELinuxProject#16 \\--> 48: ldr x0, [x0]
48: ldp x25, x26, [sp], SELinuxProject#16 \ 4c: b 0x0000000000000054
4c: ldp x21, x22, [sp], SELinuxProject#16 \ 50: mov x0, #0x0
50: ldp x19, x20, [sp], SELinuxProject#16 \---------------------------------------
54: ldp x29, x30, [sp], SELinuxProject#16 54: mov x7, #0x0
58: add x0, x7, #0x0 58: mov sp, sp
5c: autiasp 5c: ldp x27, x28, [sp], SELinuxProject#16
60: ret 60: ldp x25, x26, [sp], SELinuxProject#16
64: nop 64: ldp x21, x22, [sp], SELinuxProject#16
68: ldr x10, 0x0000000000000070 68: ldp x19, x20, [sp], SELinuxProject#16
6c: br x10 6c: ldp x29, x30, [sp], SELinuxProject#16
70: add x0, x7, #0x0
74: autiasp
78: ret
7c: nop
80: ldr x10, 0x0000000000000088
84: br x10
There are 6 extra instructions added in ARM64 in the best case. This will
become 7 in the worst case (off != 0).
RISC-V JIT (RISCV_ISA_C Disabled)
==========
No Intrumentation Verifier's Instrumentation
(upstream) (This patch)
----------------- --------------------------
0: nop 0: nop
4: nop 4: nop
8: li a6, 33 8: li a6, 33
c: addi sp, sp, -16 c: addi sp, sp, -16
10: sd s0, 8(sp) 10: sd s0, 8(sp)
14: addi s0, sp, 16 14: addi s0, sp, 16
18: ld a0, 0(a0) 18: ld a0, 0(a0)
---------------------------------------------------------------
1c: ld a0, 0(a0) --\ 1c: mv t0, a0
--------------------------\ \ 20: srli t0, t0, 32
20: li a5, 0 \ \ 24: lui t1, 4096
24: ld s0, 8(sp) \ \ 28: sext.w t1, t1
28: addi sp, sp, 16 \ \ 2c: bgeu t1, t0, 12
2c: sext.w a0, a5 \ \--> 30: ld a0, 0(a0)
30: ret \ 34: j 8
\ 38: li a0, 0
\------------------------------
3c: li a5, 0
40: ld s0, 8(sp)
44: addi sp, sp, 16
48: sext.w a0, a5
4c: ret
There are 7 extra instructions added in RISC-V.
Fixes: 8008342 ("bpf, arm64: Add BPF exception tables")
Reported-by: Breno Leitao <leitao@debian.org>
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
Link: https://lore.kernel.org/r/20240424100210.11982-2-puranjay@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
electimon
pushed a commit
to moto-common/android_kernel_motorola_msm-5.4
that referenced
this issue
Jun 6, 2024
Remove initial SIDs that have never been used or are no longer used by the kernel from its string table, which is also used to generate the SECINITSID_* symbols referenced in code. Update the code to gracefully handle the fact that these can now be NULL. Stop treating it as an error if a policy defines additional initial SIDs unknown to the kernel. Do not load unused initial SID contexts into the sidtab. Fix the incorrect usage of the name from the ocontext in error messages when loading initial SIDs since these are not presently written to the kernel policy and are therefore always NULL. After this change, it is possible to safely reclaim and reuse some of the unused initial SIDs without compatibility issues. Specifically, unused initial SIDs that were being assigned the same context as the unlabeled initial SID in policies can be reclaimed and reused for another purpose, with existing policies still treating them as having the unlabeled context and future policies having the option of mapping them to a more specific context. For example, this could have been used when the infiniband labeling support was introduced to define initial SIDs for the default pkey and endport SIDs similar to the handling of port/netif/node SIDs rather than always using SECINITSID_UNLABELED as the default. The set of safely reclaimable unused initial SIDs across all known policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod (24), policy (25), and scmp_packet (26); these initial SIDs were assigned the same context as unlabeled in all known policies including mls. If only considering non-mls policies (i.e. assuming that mls users always upgrade policy with their kernels), the set of safely reclaimable unused initial SIDs further includes file_labels (6), init (7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23). Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately became a fatal error in commit 24ed7fd ("selinux: use separate table for initial SID lookup") and even before that it could cause problems on a policy reload (collision between the new initial SID and one allocated at runtime) ever since commit 42596ea ("selinux: load the initial SIDs upon every policy load") so we cannot safely start adding new initial SIDs to policies beyond SECINITSID_NUM (27) until such a time as all such kernels do not need to be supported and only those that include this commit are relevant. That is not a big deal since we haven't added a new initial SID since 2004 (v2.6.7) and we have plenty of unused ones we can reclaim if we truly need one. If we want to avoid the wasted storage in initial_sid_to_string[] and/or sidtab->isids[] for the unused initial SIDs, we could introduce an indirection between the kernel initial SID values and the policy initial SID values and just map the policy SID values in the ocontexts to the kernel values during policy_load_isids(). Originally I thought we'd do this by preserving the initial SID names in the kernel policy and creating a mapping at load time like we do for the security classes and permissions but that would require a new kernel policy format version and associated changes to libsepol/checkpolicy and I'm not sure it is justified. Simpler approach is just to create a fixed mapping table in the kernel from the existing fixed policy values to the kernel values. Less flexible but probably sufficient. A separate selinux userspace change was applied in SELinuxProject/selinux@8677ce5 to enable removal of most of the unused initial SID contexts from policies, but there is no dependency between that change and this one. That change permits removing all of the unused initial SID contexts from policy except for the fs and sysctl SID contexts. The initial SID declarations themselves would remain in policy to preserve the values of subsequent ones but the contexts can be dropped. If/when the kernel decides to reuse one of them, future policies can change the name and start assigning a context again without breaking compatibility. Here is how I would envision staging changes to the initial SIDs in a compatible manner after this commit is applied: 1. At any time after this commit is applied, the kernel could choose to reclaim one of the safely reclaimable unused initial SIDs listed above for a new purpose (i.e. replace its NULL entry in the initial_sid_to_string[] table with a new name and start using the newly generated SECINITSID_name symbol in code), and refpolicy could at that time rename its declaration of that initial SID to reflect its new purpose and start assigning it a context going forward. Existing/old policies would map the reclaimed initial SID to the unlabeled context, so that would be the initial default behavior until policies are updated. This doesn't depend on the selinux userspace change; it will work with existing policies and userspace. 2. In 6 months or so we'll have another SELinux userspace release that will include the libsepol/checkpolicy support for omitting unused initial SID contexts. 3. At any time after that release, refpolicy can make that release its minimum build requirement and drop the sid context statements (but not the sid declarations) for all of the unused initial SIDs except for fs and sysctl, which must remain for compatibility on policy reload with old kernels and for compatibility with kernels that were still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this kernel commit; it will work with previous kernels as well. 4. After N years for some value of N, refpolicy decides that it no longer cares about policy reload compatibility for kernels that predate this kernel commit, and refpolicy drops the fs and sysctl SID contexts from policy too (but retains the declarations). 5. After M years for some value of M, the kernel decides that it no longer cares about compatibility with refpolicies that predate step 4 (dropping the fs and sysctl SIDs), and those two SIDs also become safely reclaimable. This step is optional and need not ever occur unless we decide that the need to reclaim those two SIDs outweighs the compatibility cost. 6. After O years for some value of O, refpolicy decides that it no longer cares about policy load (not just reload) compatibility for kernels that predate this kernel commit, and both kernel and refpolicy can then start adding and using new initial SIDs beyond 27. This does not depend on the previous change (step 5) and can occur independent of it. Fixes: SELinuxProject/selinux-kernel#12 Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov> Signed-off-by: Paul Moore <paul@paul-moore.com>
Notkerd69
pushed a commit
to Keret-Playground/kernel_motorola_rhodep
that referenced
this issue
Jul 25, 2024
Remove initial SIDs that have never been used or are no longer used by the kernel from its string table, which is also used to generate the SECINITSID_* symbols referenced in code. Update the code to gracefully handle the fact that these can now be NULL. Stop treating it as an error if a policy defines additional initial SIDs unknown to the kernel. Do not load unused initial SID contexts into the sidtab. Fix the incorrect usage of the name from the ocontext in error messages when loading initial SIDs since these are not presently written to the kernel policy and are therefore always NULL. After this change, it is possible to safely reclaim and reuse some of the unused initial SIDs without compatibility issues. Specifically, unused initial SIDs that were being assigned the same context as the unlabeled initial SID in policies can be reclaimed and reused for another purpose, with existing policies still treating them as having the unlabeled context and future policies having the option of mapping them to a more specific context. For example, this could have been used when the infiniband labeling support was introduced to define initial SIDs for the default pkey and endport SIDs similar to the handling of port/netif/node SIDs rather than always using SECINITSID_UNLABELED as the default. The set of safely reclaimable unused initial SIDs across all known policies is igmp_packet (13), icmp_socket (14), tcp_socket (15), kmod (24), policy (25), and scmp_packet (26); these initial SIDs were assigned the same context as unlabeled in all known policies including mls. If only considering non-mls policies (i.e. assuming that mls users always upgrade policy with their kernels), the set of safely reclaimable unused initial SIDs further includes file_labels (6), init (7), sysctl_modprobe (16), and sysctl_fs (18) through sysctl_dev (23). Adding new initial SIDs beyond SECINITSID_NUM to policy unfortunately became a fatal error in commit 24ed7fd ("selinux: use separate table for initial SID lookup") and even before that it could cause problems on a policy reload (collision between the new initial SID and one allocated at runtime) ever since commit 42596ea ("selinux: load the initial SIDs upon every policy load") so we cannot safely start adding new initial SIDs to policies beyond SECINITSID_NUM (27) until such a time as all such kernels do not need to be supported and only those that include this commit are relevant. That is not a big deal since we haven't added a new initial SID since 2004 (v2.6.7) and we have plenty of unused ones we can reclaim if we truly need one. If we want to avoid the wasted storage in initial_sid_to_string[] and/or sidtab->isids[] for the unused initial SIDs, we could introduce an indirection between the kernel initial SID values and the policy initial SID values and just map the policy SID values in the ocontexts to the kernel values during policy_load_isids(). Originally I thought we'd do this by preserving the initial SID names in the kernel policy and creating a mapping at load time like we do for the security classes and permissions but that would require a new kernel policy format version and associated changes to libsepol/checkpolicy and I'm not sure it is justified. Simpler approach is just to create a fixed mapping table in the kernel from the existing fixed policy values to the kernel values. Less flexible but probably sufficient. A separate selinux userspace change was applied in SELinuxProject/selinux@8677ce5 to enable removal of most of the unused initial SID contexts from policies, but there is no dependency between that change and this one. That change permits removing all of the unused initial SID contexts from policy except for the fs and sysctl SID contexts. The initial SID declarations themselves would remain in policy to preserve the values of subsequent ones but the contexts can be dropped. If/when the kernel decides to reuse one of them, future policies can change the name and start assigning a context again without breaking compatibility. Here is how I would envision staging changes to the initial SIDs in a compatible manner after this commit is applied: 1. At any time after this commit is applied, the kernel could choose to reclaim one of the safely reclaimable unused initial SIDs listed above for a new purpose (i.e. replace its NULL entry in the initial_sid_to_string[] table with a new name and start using the newly generated SECINITSID_name symbol in code), and refpolicy could at that time rename its declaration of that initial SID to reflect its new purpose and start assigning it a context going forward. Existing/old policies would map the reclaimed initial SID to the unlabeled context, so that would be the initial default behavior until policies are updated. This doesn't depend on the selinux userspace change; it will work with existing policies and userspace. 2. In 6 months or so we'll have another SELinux userspace release that will include the libsepol/checkpolicy support for omitting unused initial SID contexts. 3. At any time after that release, refpolicy can make that release its minimum build requirement and drop the sid context statements (but not the sid declarations) for all of the unused initial SIDs except for fs and sysctl, which must remain for compatibility on policy reload with old kernels and for compatibility with kernels that were still using SECINITSID_SYSCTL (< 2.6.39). This doesn't depend on this kernel commit; it will work with previous kernels as well. 4. After N years for some value of N, refpolicy decides that it no longer cares about policy reload compatibility for kernels that predate this kernel commit, and refpolicy drops the fs and sysctl SID contexts from policy too (but retains the declarations). 5. After M years for some value of M, the kernel decides that it no longer cares about compatibility with refpolicies that predate step 4 (dropping the fs and sysctl SIDs), and those two SIDs also become safely reclaimable. This step is optional and need not ever occur unless we decide that the need to reclaim those two SIDs outweighs the compatibility cost. 6. After O years for some value of O, refpolicy decides that it no longer cares about policy load (not just reload) compatibility for kernels that predate this kernel commit, and both kernel and refpolicy can then start adding and using new initial SIDs beyond 27. This does not depend on the previous change (step 5) and can occur independent of it. Fixes: SELinuxProject/selinux-kernel#12 Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov> Signed-off-by: Paul Moore <paul@paul-moore.com>
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We need dynamic discovery of initial SIDs to fix this problem. Similar to dynamic discovery of classes/perms, map kernel initial SIDs to policy initial SIDs by string name rather than requiring identical index values, handle unknown initial SIDs cleanly (map to unlabeled), and allow future extensibility without causing problems (start regular SIDs at some fixed offset, e.g. 100, or start from the highest legal value and decrement, so that policy reload that changes the number of initial SIDs won't affect them). Even with this, we'll be limited by compatibility for a while until kernels without this feature are so old they no longer matter, but otherwise we'll never be free of it.
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