perf: Fix NULL deref

Dan reported:

  1229                  if (ctx->task == TASK_TOMBSTONE ||
  1230                      !atomic_inc_not_zero(&ctx->refcount)) {
  1231                          raw_spin_unlock(&ctx->lock);
  1232                          ctx = NULL;
                                ^^^^^^^^^^
ctx is NULL.

  1233                  }
  1234
  1235                  WARN_ON_ONCE(ctx->task != task);
                                     ^^^^^^^^^^^^^^^^^
The patch adds a NULL dereference.

Reported-by: Dan Carpenter <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vince Weaver <[email protected]>
Fixes: 63b6da39bb ("perf: Fix perf_event_exit_task() race")
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Peter Zijlstra 2016-01-27 21:59:04 +01:00 • committed by Ingo Molnar
commit 828b6f0e26

View file

@ -1230,9 +1230,9 @@ retry:
!atomic_inc_not_zero(&ctx->refcount)) {
raw_spin_unlock(&ctx->lock);
ctx = NULL;
} else {
WARN_ON_ONCE(ctx->task != task);
}
WARN_ON_ONCE(ctx->task != task);
}
rcu_read_unlock();
if (!ctx)