Revision 2aeb1883547626d82c597cce2c99f0b9c62e2425 authored by Jiri Olsa on 20 July 2017, 14:14:55 UTC, committed by Ingo Molnar on 21 July 2017, 07:54:23 UTC
We're missing ctx lock when iterating children siblings within the perf_read path for group reading. Following race and crash can happen: User space doing read syscall on event group leader: T1: perf_read lock event->ctx->mutex perf_read_group lock leader->child_mutex __perf_read_group_add(child) list_for_each_entry(sub, &leader->sibling_list, group_entry) ----> sub might be invalid at this point, because it could get removed via perf_event_exit_task_context in T2 Child exiting and cleaning up its events: T2: perf_event_exit_task_context lock ctx->mutex list_for_each_entry_safe(child_event, next, &child_ctx->event_list,... perf_event_exit_event(child) lock ctx->lock perf_group_detach(child) unlock ctx->lock ----> child is removed from sibling_list without any sync with T1 path above ... free_event(child) Before the child is removed from the leader's child_list, (and thus is omitted from perf_read_group processing), we need to ensure that perf_read_group touches child's siblings under its ctx->lock. Peter further notes: | One additional note; this bug got exposed by commit: | | ba5213ae6b88 ("perf/core: Correct event creation with PERF_FORMAT_GROUP") | | which made it possible to actually trigger this code-path. Tested-by: Andi Kleen <ak@linux.intel.com> Signed-off-by: Jiri Olsa <jolsa@kernel.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: ba5213ae6b88 ("perf/core: Correct event creation with PERF_FORMAT_GROUP") Link: http://lkml.kernel.org/r/20170720141455.2106-1-jolsa@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Makefile | -rw-r--r-- | 4.2 KB |
aio.c | -rw-r--r-- | 46.2 KB |
anon_inodes.c | -rw-r--r-- | 4.9 KB |
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bad_inode.c | -rw-r--r-- | 5.3 KB |
binfmt_aout.c | -rw-r--r-- | 10.8 KB |
binfmt_elf.c | -rw-r--r-- | 61.3 KB |
binfmt_elf_fdpic.c | -rw-r--r-- | 47.0 KB |
binfmt_em86.c | -rw-r--r-- | 2.8 KB |
binfmt_flat.c | -rw-r--r-- | 27.9 KB |
binfmt_misc.c | -rw-r--r-- | 18.3 KB |
binfmt_script.c | -rw-r--r-- | 3.0 KB |
block_dev.c | -rw-r--r-- | 53.2 KB |
buffer.c | -rw-r--r-- | 91.3 KB |
char_dev.c | -rw-r--r-- | 16.1 KB |
compat.c | -rw-r--r-- | 5.1 KB |
compat_binfmt_elf.c | -rw-r--r-- | 3.4 KB |
compat_ioctl.c | -rw-r--r-- | 45.8 KB |
coredump.c | -rw-r--r-- | 21.3 KB |
dax.c | -rw-r--r-- | 41.2 KB |
dcache.c | -rw-r--r-- | 93.9 KB |
dcookies.c | -rw-r--r-- | 6.9 KB |
direct-io.c | -rw-r--r-- | 38.5 KB |
drop_caches.c | -rw-r--r-- | 1.6 KB |
eventfd.c | -rw-r--r-- | 12.9 KB |
eventpoll.c | -rw-r--r-- | 62.2 KB |
exec.c | -rw-r--r-- | 45.1 KB |
fcntl.c | -rw-r--r-- | 22.0 KB |
fhandle.c | -rw-r--r-- | 6.8 KB |
file.c | -rw-r--r-- | 23.6 KB |
file_table.c | -rw-r--r-- | 8.6 KB |
filesystems.c | -rw-r--r-- | 6.4 KB |
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inode.c | -rw-r--r-- | 55.0 KB |
internal.h | -rw-r--r-- | 4.6 KB |
ioctl.c | -rw-r--r-- | 17.3 KB |
iomap.c | -rw-r--r-- | 22.9 KB |
libfs.c | -rw-r--r-- | 30.5 KB |
locks.c | -rw-r--r-- | 73.3 KB |
mbcache.c | -rw-r--r-- | 11.9 KB |
mount.h | -rw-r--r-- | 3.7 KB |
mpage.c | -rw-r--r-- | 20.6 KB |
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namespace.c | -rw-r--r-- | 85.4 KB |
no-block.c | -rw-r--r-- | 688 bytes |
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posix_acl.c | -rw-r--r-- | 21.4 KB |
proc_namespace.c | -rw-r--r-- | 7.8 KB |
read_write.c | -rw-r--r-- | 47.0 KB |
readdir.c | -rw-r--r-- | 11.2 KB |
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timerfd.c | -rw-r--r-- | 13.4 KB |
userfaultfd.c | -rw-r--r-- | 47.9 KB |
utimes.c | -rw-r--r-- | 7.1 KB |
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