perf: Fix use after free in perf_remove_from_context()
authorPeter Zijlstra <peterz@infradead.org>
Thu, 29 May 2014 17:00:24 +0000 (19:00 +0200)
committerIngo Molnar <mingo@kernel.org>
Thu, 5 Jun 2014 10:29:52 +0000 (12:29 +0200)
commitebf905fc7a6e7c99c53b5afc888d8f950da90aff
tree9b0c9289f1ac0f30fe14f9bb5a6a646023134f66
parent10b0256496fd6c162478547f7c6df1e052e87644
perf: Fix use after free in perf_remove_from_context()

While that mutex should guard the elements, it doesn't guard against the
use-after-free that's from list_for_each_entry_rcu().
__perf_event_exit_task() can actually free the event.

And because list addition/deletion is guarded by both ctx->mutex and
ctx->lock, holding ctx->mutex is sufficient for reading the list, so we
don't actually need the rcu list iteration.

Fixes: 3a497f48637e ("perf: Simplify perf_event_exit_task_context()")
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Tested-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Jones <davej@redhat.com>
Cc: acme@ghostprotocols.net
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140529170024.GA2315@laptop.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
kernel/events/core.c