CUnseal sets global permission incorrectly if cd and ct are the same register #24
Comments
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I have updated the CHERI Architecture document to make it clear what should happen in this case, and have added a regression test to the test suite. |
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Fixed with the following change: 30fd38d |
arichardson
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All paths that lead to bdrv_backup_top_drop(), except for the call
from backup_clean(), imply that the BDS AioContext has already been
acquired, so doing it there too can potentially lead to QEMU hanging
on AIO_WAIT_WHILE().
An easy way to trigger this situation is by issuing a two actions
transaction, with a proper and a bogus blockdev-backup, so the second
one will trigger a rollback. This will trigger a hang with an stack
trace like this one:
#0 0x00007fb680c75016 in __GI_ppoll (fds=0x55e74580f7c0, nfds=1, timeout=<optimized out>,
timeout@entry=0x0, sigmask=sigmask@entry=0x0) at ../sysdeps/unix/sysv/linux/ppoll.c:39
#1 0x000055e743386e09 in ppoll (__ss=0x0, __timeout=0x0, __nfds=<optimized out>, __fds=<optimized out>)
at /usr/include/bits/poll2.h:77
#2 0x000055e743386e09 in qemu_poll_ns
(fds=<optimized out>, nfds=<optimized out>, timeout=<optimized out>) at util/qemu-timer.c:336
#3 0x000055e743388dc4 in aio_poll (ctx=0x55e7458925d0, blocking=blocking@entry=true)
at util/aio-posix.c:669
#4 0x000055e743305dea in bdrv_flush (bs=bs@entry=0x55e74593c0d0) at block/io.c:2878
#5 0x000055e7432be58e in bdrv_close (bs=0x55e74593c0d0) at block.c:4017
#6 0x000055e7432be58e in bdrv_delete (bs=<optimized out>) at block.c:4262
#7 0x000055e7432be58e in bdrv_unref (bs=bs@entry=0x55e74593c0d0) at block.c:5644
#8 0x000055e743316b9b in bdrv_backup_top_drop (bs=bs@entry=0x55e74593c0d0) at block/backup-top.c:273
#9 0x000055e74331461f in backup_job_create
(job_id=0x0, bs=bs@entry=0x55e7458d5820, target=target@entry=0x55e74589f640, speed=0, sync_mode=MIRROR_SYNC_MODE_FULL, sync_bitmap=sync_bitmap@entry=0x0, bitmap_mode=BITMAP_SYNC_MODE_ON_SUCCESS, compress=false, filter_node_name=0x0, on_source_error=BLOCKDEV_ON_ERROR_REPORT, on_target_error=BLOCKDEV_ON_ERROR_REPORT, creation_flags=0, cb=0x0, opaque=0x0, txn=0x0, errp=0x7ffddfd1efb0) at block/backup.c:478
#10 0x000055e74315bc52 in do_backup_common
(backup=backup@entry=0x55e746c066d0, bs=bs@entry=0x55e7458d5820, target_bs=target_bs@entry=0x55e74589f640, aio_context=aio_context@entry=0x55e7458a91e0, txn=txn@entry=0x0, errp=errp@entry=0x7ffddfd1efb0)
at blockdev.c:3580
#11 0x000055e74315c37c in do_blockdev_backup
(backup=backup@entry=0x55e746c066d0, txn=0x0, errp=errp@entry=0x7ffddfd1efb0)
at /usr/src/debug/qemu-kvm-4.2.0-2.module+el8.2.0+5135+ed3b2489.x86_64/./qapi/qapi-types-block-core.h:1492
#12 0x000055e74315c449 in blockdev_backup_prepare (common=0x55e746a8de90, errp=0x7ffddfd1f018)
at blockdev.c:1885
#13 0x000055e743160152 in qmp_transaction
(dev_list=<optimized out>, has_props=<optimized out>, props=0x55e7467fe2c0, errp=errp@entry=0x7ffddfd1f088) at blockdev.c:2340
#14 0x000055e743287ff5 in qmp_marshal_transaction
(args=<optimized out>, ret=<optimized out>, errp=0x7ffddfd1f0f8)
at qapi/qapi-commands-transaction.c:44
#15 0x000055e74333de6c in do_qmp_dispatch
(errp=0x7ffddfd1f0f0, allow_oob=<optimized out>, request=<optimized out>, cmds=0x55e743c28d60 <qmp_commands>) at qapi/qmp-dispatch.c:132
#16 0x000055e74333de6c in qmp_dispatch
(cmds=0x55e743c28d60 <qmp_commands>, request=<optimized out>, allow_oob=<optimized out>)
at qapi/qmp-dispatch.c:175
#17 0x000055e74325c061 in monitor_qmp_dispatch (mon=0x55e745908030, req=<optimized out>)
at monitor/qmp.c:145
#18 0x000055e74325c6fa in monitor_qmp_bh_dispatcher (data=<optimized out>) at monitor/qmp.c:234
#19 0x000055e743385866 in aio_bh_call (bh=0x55e745807ae0) at util/async.c:117
#20 0x000055e743385866 in aio_bh_poll (ctx=ctx@entry=0x55e7458067a0) at util/async.c:117
#21 0x000055e743388c54 in aio_dispatch (ctx=0x55e7458067a0) at util/aio-posix.c:459
#22 0x000055e743385742 in aio_ctx_dispatch
(source=<optimized out>, callback=<optimized out>, user_data=<optimized out>) at util/async.c:260
#23 0x00007fb68543e67d in g_main_dispatch (context=0x55e745893a40) at gmain.c:3176
#24 0x00007fb68543e67d in g_main_context_dispatch (context=context@entry=0x55e745893a40) at gmain.c:3829
#25 0x000055e743387d08 in glib_pollfds_poll () at util/main-loop.c:219
#26 0x000055e743387d08 in os_host_main_loop_wait (timeout=<optimized out>) at util/main-loop.c:242
#27 0x000055e743387d08 in main_loop_wait (nonblocking=<optimized out>) at util/main-loop.c:518
#28 0x000055e74316a3c1 in main_loop () at vl.c:1828
#29 0x000055e743016a72 in main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>)
at vl.c:4504
Fix this by not acquiring the AioContext there, and ensuring all paths
leading to it have it already acquired (backup_clean()).
RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1782111
Signed-off-by: Sergio Lopez <slp@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
arichardson
pushed a commit
that referenced
this issue
Jan 29, 2020
external_snapshot_abort() calls to bdrv_set_backing_hd(), which returns state->old_bs to the main AioContext, as it's intended to be used then the BDS is going to be released. As that's not the case when aborting an external snapshot, return it to the AioContext it was before the call. This issue can be triggered by issuing a transaction with two actions, a proper blockdev-snapshot-sync and a bogus one, so the second will trigger a transaction abort. This results in a crash with an stack trace like this one: #0 0x00007fa1048b28df in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50 #1 0x00007fa10489ccf5 in __GI_abort () at abort.c:79 #2 0x00007fa10489cbc9 in __assert_fail_base (fmt=0x7fa104a03300 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n", assertion=0x5572240b44d8 "bdrv_get_aio_context(old_bs) == bdrv_get_aio_context(new_bs)", file=0x557224014d30 "block.c", line=2240, function=<optimized out>) at assert.c:92 #3 0x00007fa1048aae96 in __GI___assert_fail (assertion=assertion@entry=0x5572240b44d8 "bdrv_get_aio_context(old_bs) == bdrv_get_aio_context(new_bs)", file=file@entry=0x557224014d30 "block.c", line=line@entry=2240, function=function@entry=0x5572240b5d60 <__PRETTY_FUNCTION__.31620> "bdrv_replace_child_noperm") at assert.c:101 #4 0x0000557223e631f8 in bdrv_replace_child_noperm (child=0x557225b9c980, new_bs=new_bs@entry=0x557225c42e40) at block.c:2240 #5 0x0000557223e68be7 in bdrv_replace_node (from=0x557226951a60, to=0x557225c42e40, errp=0x5572247d6138 <error_abort>) at block.c:4196 #6 0x0000557223d069c4 in external_snapshot_abort (common=0x557225d7e170) at blockdev.c:1731 #7 0x0000557223d069c4 in external_snapshot_abort (common=0x557225d7e170) at blockdev.c:1717 #8 0x0000557223d09013 in qmp_transaction (dev_list=<optimized out>, has_props=<optimized out>, props=0x557225cc7d70, errp=errp@entry=0x7ffe704c0c98) at blockdev.c:2360 #9 0x0000557223e32085 in qmp_marshal_transaction (args=<optimized out>, ret=<optimized out>, errp=0x7ffe704c0d08) at qapi/qapi-commands-transaction.c:44 #10 0x0000557223ee798c in do_qmp_dispatch (errp=0x7ffe704c0d00, allow_oob=<optimized out>, request=<optimized out>, cmds=0x5572247d3cc0 <qmp_commands>) at qapi/qmp-dispatch.c:132 #11 0x0000557223ee798c in qmp_dispatch (cmds=0x5572247d3cc0 <qmp_commands>, request=<optimized out>, allow_oob=<optimized out>) at qapi/qmp-dispatch.c:175 #12 0x0000557223e06141 in monitor_qmp_dispatch (mon=0x557225c69ff0, req=<optimized out>) at monitor/qmp.c:120 #13 0x0000557223e0678a in monitor_qmp_bh_dispatcher (data=<optimized out>) at monitor/qmp.c:209 #14 0x0000557223f2f366 in aio_bh_call (bh=0x557225b9dc60) at util/async.c:117 #15 0x0000557223f2f366 in aio_bh_poll (ctx=ctx@entry=0x557225b9c840) at util/async.c:117 #16 0x0000557223f32754 in aio_dispatch (ctx=0x557225b9c840) at util/aio-posix.c:459 #17 0x0000557223f2f242 in aio_ctx_dispatch (source=<optimized out>, callback=<optimized out>, user_data=<optimized out>) at util/async.c:260 #18 0x00007fa10913467d in g_main_dispatch (context=0x557225c28e80) at gmain.c:3176 #19 0x00007fa10913467d in g_main_context_dispatch (context=context@entry=0x557225c28e80) at gmain.c:3829 #20 0x0000557223f31808 in glib_pollfds_poll () at util/main-loop.c:219 #21 0x0000557223f31808 in os_host_main_loop_wait (timeout=<optimized out>) at util/main-loop.c:242 #22 0x0000557223f31808 in main_loop_wait (nonblocking=<optimized out>) at util/main-loop.c:518 #23 0x0000557223d13201 in main_loop () at vl.c:1828 #24 0x0000557223bbfb82 in main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at vl.c:4504 RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1779036 Signed-off-by: Sergio Lopez <slp@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
arichardson
pushed a commit
to arichardson/qemu
that referenced
this issue
Apr 15, 2020
There is a use-after-free possible: bdrv_unref_child() leaves
bs->backing freed but not NULL. bdrv_attach_child may produce nested
polling loop due to drain, than access of freed pointer is possible.
I've produced the following crash on 30 iotest with modified code. It
does not reproduce on master, but still seems possible:
#0 __strcmp_avx2 () at /lib64/libc.so.6
CTSRD-CHERI#1 bdrv_backing_overridden (bs=0x55c9d3cc2060) at block.c:6350
CTSRD-CHERI#2 bdrv_refresh_filename (bs=0x55c9d3cc2060) at block.c:6404
CTSRD-CHERI#3 bdrv_backing_attach (c=0x55c9d48e5520) at block.c:1063
CTSRD-CHERI#4 bdrv_replace_child_noperm
(child=child@entry=0x55c9d48e5520,
new_bs=new_bs@entry=0x55c9d3cc2060) at block.c:2290
CTSRD-CHERI#5 bdrv_replace_child
(child=child@entry=0x55c9d48e5520,
new_bs=new_bs@entry=0x55c9d3cc2060) at block.c:2320
CTSRD-CHERI#6 bdrv_root_attach_child
(child_bs=child_bs@entry=0x55c9d3cc2060,
child_name=child_name@entry=0x55c9d241d478 "backing",
child_role=child_role@entry=0x55c9d26ecee0 <child_backing>,
ctx=<optimized out>, perm=<optimized out>, shared_perm=21,
opaque=0x55c9d3c5a3d0, errp=0x7ffd117108e0) at block.c:2424
CTSRD-CHERI#7 bdrv_attach_child
(parent_bs=parent_bs@entry=0x55c9d3c5a3d0,
child_bs=child_bs@entry=0x55c9d3cc2060,
child_name=child_name@entry=0x55c9d241d478 "backing",
child_role=child_role@entry=0x55c9d26ecee0 <child_backing>,
errp=errp@entry=0x7ffd117108e0) at block.c:5876
CTSRD-CHERI#8 in bdrv_set_backing_hd
(bs=bs@entry=0x55c9d3c5a3d0,
backing_hd=backing_hd@entry=0x55c9d3cc2060,
errp=errp@entry=0x7ffd117108e0)
at block.c:2576
CTSRD-CHERI#9 stream_prepare (job=0x55c9d49d84a0) at block/stream.c:150
CTSRD-CHERI#10 job_prepare (job=0x55c9d49d84a0) at job.c:761
CTSRD-CHERI#11 job_txn_apply (txn=<optimized out>, fn=<optimized out>) at
job.c:145
CTSRD-CHERI#12 job_do_finalize (job=0x55c9d49d84a0) at job.c:778
CTSRD-CHERI#13 job_completed_txn_success (job=0x55c9d49d84a0) at job.c:832
CTSRD-CHERI#14 job_completed (job=0x55c9d49d84a0) at job.c:845
CTSRD-CHERI#15 job_completed (job=0x55c9d49d84a0) at job.c:836
CTSRD-CHERI#16 job_exit (opaque=0x55c9d49d84a0) at job.c:864
CTSRD-CHERI#17 aio_bh_call (bh=0x55c9d471a160) at util/async.c:117
CTSRD-CHERI#18 aio_bh_poll (ctx=ctx@entry=0x55c9d3c46720) at util/async.c:117
CTSRD-CHERI#19 aio_poll (ctx=ctx@entry=0x55c9d3c46720,
blocking=blocking@entry=true)
at util/aio-posix.c:728
CTSRD-CHERI#20 bdrv_parent_drained_begin_single (poll=true, c=0x55c9d3d558f0)
at block/io.c:121
CTSRD-CHERI#21 bdrv_parent_drained_begin_single (c=c@entry=0x55c9d3d558f0,
poll=poll@entry=true)
at block/io.c:114
CTSRD-CHERI#22 bdrv_replace_child_noperm
(child=child@entry=0x55c9d3d558f0,
new_bs=new_bs@entry=0x55c9d3d27300) at block.c:2258
CTSRD-CHERI#23 bdrv_replace_child
(child=child@entry=0x55c9d3d558f0,
new_bs=new_bs@entry=0x55c9d3d27300) at block.c:2320
CTSRD-CHERI#24 bdrv_root_attach_child
(child_bs=child_bs@entry=0x55c9d3d27300,
child_name=child_name@entry=0x55c9d241d478 "backing",
child_role=child_role@entry=0x55c9d26ecee0 <child_backing>,
ctx=<optimized out>, perm=<optimized out>, shared_perm=21,
opaque=0x55c9d3cc2060, errp=0x7ffd11710c60) at block.c:2424
CTSRD-CHERI#25 bdrv_attach_child
(parent_bs=parent_bs@entry=0x55c9d3cc2060,
child_bs=child_bs@entry=0x55c9d3d27300,
child_name=child_name@entry=0x55c9d241d478 "backing",
child_role=child_role@entry=0x55c9d26ecee0 <child_backing>,
errp=errp@entry=0x7ffd11710c60) at block.c:5876
CTSRD-CHERI#26 bdrv_set_backing_hd
(bs=bs@entry=0x55c9d3cc2060,
backing_hd=backing_hd@entry=0x55c9d3d27300,
errp=errp@entry=0x7ffd11710c60)
at block.c:2576
CTSRD-CHERI#27 stream_prepare (job=0x55c9d495ead0) at block/stream.c:150
...
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20200316060631.30052-2-vsementsov@virtuozzo.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
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The implementation overwrites the destination before calculating whether to set the permission based on
ct. Example in L3 where the permission is not set:and in qemu it sets the permission:
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