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bpf: Fix the release of inner map #5979

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bpf: Fix the release of inner map #5979

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kernel-patches-daemon-bpf[bot]
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Pull request for series with
subject: bpf: Fix the release of inner map
version: 2
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=800633

@kernel-patches-daemon-bpf
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Upstream branch: e2e57d6
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=800633
version: 2

@kernel-patches-daemon-bpf
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Upstream branch: 1fda5bb
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=800633
version: 2

@kernel-patches-daemon-bpf
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Upstream branch: 7475e51
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=800633
version: 2

Hou Tao added 5 commits November 18, 2023 09:43
bpf: Check rcu_read_lock_trace_held() before calling bpf map helpers
241a6a2 
These three bpf_map_{lookup,update,delete}_elem() helpers are also
available for sleepable bpf program, so add the corresponding lock
assertion for sleepable bpf program, otherwise the following warning
will be reported when a sleepable bpf program manipulates bpf map under
interpreter mode (aka bpf_jit_enable=0):

  WARNING: CPU: 3 PID: 4985 at kernel/bpf/helpers.c:40 ......
  CPU: 3 PID: 4985 Comm: test_progs Not tainted 6.6.0+ #2
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) ......
  RIP: 0010:bpf_map_lookup_elem+0x54/0x60
  ......
  Call Trace:
   <TASK>
   ? __warn+0xa5/0x240
   ? bpf_map_lookup_elem+0x54/0x60
   ? report_bug+0x1ba/0x1f0
   ? handle_bug+0x40/0x80
   ? exc_invalid_op+0x18/0x50
   ? asm_exc_invalid_op+0x1b/0x20
   ? __pfx_bpf_map_lookup_elem+0x10/0x10
   ? rcu_lockdep_current_cpu_online+0x65/0xb0
   ? rcu_is_watching+0x23/0x50
   ? bpf_map_lookup_elem+0x54/0x60
   ? __pfx_bpf_map_lookup_elem+0x10/0x10
   ___bpf_prog_run+0x513/0x3b70
   __bpf_prog_run32+0x9d/0xd0
   ? __bpf_prog_enter_sleepable_recur+0xad/0x120
   ? __bpf_prog_enter_sleepable_recur+0x3e/0x120
   bpf_trampoline_6442580665+0x4d/0x1000
   __x64_sys_getpgid+0x5/0x30
   ? do_syscall_64+0x36/0xb0
   entry_SYSCALL_64_after_hwframe+0x6e/0x76
   </TASK>

Signed-off-by: Hou Tao <houtao1@huawei.com>
bpf: Add map and need_defer parameters to .map_fd_put_ptr()
4a974da 
map is the pointer of outer map, and need_defer needs some explanation.
need_defer tells the implementation to defer the reference release of
the passed element and ensure that the element is still alive before
the bpf program, which may manipulate it, exits.

The following three cases will invoke map_fd_put_ptr() and different
need_defer values will be passed to these callers:

1) release the reference of the old element in the map during map update
   or map deletion. The release must be deferred, otherwise the bpf
   program may incur use-after-free problem, so need_defer needs to be
   true.
2) release the reference of the to-be-added element in the error path of
   map update. The to-be-added element is not visible to any bpf
   program, so it is OK to pass false for need_defer parameter.
3) release the references of all elements in the map during map release.
   Any bpf program which has access to the map must have been exited and
   released, so need_defer=false will be OK.

These two parameters will be used by the following patches to fix the
potential use-after-free problem for map-in-map.

Signed-off-by: Hou Tao <houtao1@huawei.com>
bpf: Defer the free of inner map when necessary
b89987b 
When updating or deleting an inner map in map array or map htab, the map
may still be accessed by non-sleepable program or sleepable program.
However bpf_map_fd_put_ptr() decreases the ref-count of the inner map
directly through bpf_map_put(), if the ref-count is the last ref-count
(which is true for most cases), the inner map will be free by
ops->map_free() in a kworker. But for now, most .map_free() callbacks
don't use synchronize_rcu() or its variants to wait for the elapse of a
RCU grace period, so after the invocation of ops->map_free completes,
the bpf program which is accessing the inner map may incur
use-after-free problem.

Fix it by telling bpf_map_free_deferred() to wait for both one RCU grace
period and one tasks trace RCU grace period before calling
ops->map_free() for inner map.

Fixes: bba1dc0 ("bpf: Remove redundant synchronize_rcu.")
Fixes: 638e4b8 ("bpf: Allows per-cpu maps and map-in-map in sleepable programs")
Signed-off-by: Hou Tao <houtao1@huawei.com>
bpf: Optimize the free of inner map
0d37e23 
When removing the inner map from the outer map, the inner map will be
freed after one RCU grace period and one RCU tasks trace grace
period, so it is certain that the bpf program which may access the inner
map, has exited before the inner map is freed.

However there is unnecessary to wait for one RCU grace period or one RCU
tasks trace grace period if the outer map is only accessed by sleepable
program or non-sleepable program. So recording the context of the owned
bpf programs when adding map into env->used_maps and using the recorded
access context to decide which, and how many, RCU grace periods are
needed when freeing the inner map.

Signed-off-by: Hou Tao <houtao1@huawei.com>
selftests/bpf: Add test cases for inner map
b621a36 
Add test cases to test the race between the destroy of inner map due to
map-in-map update and the access of inner map in bpf program. The
following 4 combination are added:
(1) array map in map array + bpf program
(2) array map in map array + sleepable bpf program
(3) array map in map htab + bpf program
(4) array map in map htab + sleepable bpf program

Before applying the fixes, when running `./test_prog -a map_in_map`, the
following error was reported:

  ==================================================================
  BUG: KASAN: slab-use-after-free in array_map_update_elem+0x48/0x3e0
  Read of size 4 at addr ffff888114f33824 by task test_progs/1858

  CPU: 1 PID: 1858 Comm: test_progs Tainted: G           O     6.6.0+ #7
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) ......
  Call Trace:
   <TASK>
   dump_stack_lvl+0x4a/0x90
   print_report+0xd2/0x620
   kasan_report+0xd1/0x110
   __asan_load4+0x81/0xa0
   array_map_update_elem+0x48/0x3e0
   bpf_prog_be94a9f26772f5b7_access_map_in_array+0xe6/0xf6
   trace_call_bpf+0x1aa/0x580
   kprobe_perf_func+0xdd/0x430
   kprobe_dispatcher+0xa0/0xb0
   kprobe_ftrace_handler+0x18b/0x2e0
   0xffffffffc02280f7
  RIP: 0010:__x64_sys_getpgid+0x1/0x30
  ......
   </TASK>

  Allocated by task 1857:
   kasan_save_stack+0x26/0x50
   kasan_set_track+0x25/0x40
   kasan_save_alloc_info+0x1e/0x30
   __kasan_kmalloc+0x98/0xa0
   __kmalloc_node+0x6a/0x150
   __bpf_map_area_alloc+0x141/0x170
   bpf_map_area_alloc+0x10/0x20
   array_map_alloc+0x11f/0x310
   map_create+0x28a/0xb40
   __sys_bpf+0x753/0x37c0
   __x64_sys_bpf+0x44/0x60
   do_syscall_64+0x36/0xb0
   entry_SYSCALL_64_after_hwframe+0x6e/0x76

  Freed by task 11:
   kasan_save_stack+0x26/0x50
   kasan_set_track+0x25/0x40
   kasan_save_free_info+0x2b/0x50
   __kasan_slab_free+0x113/0x190
   slab_free_freelist_hook+0xd7/0x1e0
   __kmem_cache_free+0x170/0x260
   kfree+0x9b/0x160
   kvfree+0x2d/0x40
   bpf_map_area_free+0xe/0x20
   array_map_free+0x120/0x2c0
   bpf_map_free_deferred+0xd7/0x1e0
   process_one_work+0x462/0x990
   worker_thread+0x370/0x670
   kthread+0x1b0/0x200
   ret_from_fork+0x3a/0x70
   ret_from_fork_asm+0x1b/0x30

  Last potentially related work creation:
   kasan_save_stack+0x26/0x50
   __kasan_record_aux_stack+0x94/0xb0
   kasan_record_aux_stack_noalloc+0xb/0x20
   __queue_work+0x331/0x950
   queue_work_on+0x75/0x80
   bpf_map_put+0xfa/0x160
   bpf_map_fd_put_ptr+0xe/0x20
   bpf_fd_array_map_update_elem+0x174/0x1b0
   bpf_map_update_value+0x2b7/0x4a0
   __sys_bpf+0x2551/0x37c0
   __x64_sys_bpf+0x44/0x60
   do_syscall_64+0x36/0xb0
   entry_SYSCALL_64_after_hwframe+0x6e/0x76

Signed-off-by: Hou Tao <houtao1@huawei.com>
@kernel-patches-daemon-bpf
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Upstream branch: 76df934
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=800633
version: 2

@kernel-patches-daemon-bpf
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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=800633 expired. Closing PR.

@kernel-patches-daemon-bpf kernel-patches-daemon-bpf bot deleted the series/799448=>bpf branch November 23, 2023 00:16
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