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futex: Fix handling of bad requeue syscall pairing 

If futex_requeue(requeue_pi=1) finds a futex_q that was created by a call
other the futex_wait_requeue_pi(), the q.rt_waiter may be null.  If so,
this will result in an oops from the following call graph:

futex_requeue()
  rt_mutex_start_proxy_lock()
    task_blocks_on_rt_mutex()
      waiter->task dereference
        OOPS

We currently WARN_ON() if this is detected, clearly this is inadequate.
If we detect a mispairing in futex_requeue(), bail out, seding -EINVAL to
user-space.

V2: Fix parenthesis warnings.

Signed-off-by: Darren Hart <dvhltc@us.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: John Kacur <jkacur@redhat.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Dinakar Guniguntala <dino@in.ibm.com>
Cc: John Stultz <johnstul@linux.vnet.ibm.com>
LKML-Reference: <4A7CA8C0.7010809@us.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Darren Hart 2009-08-07 15:20:48 -07:00 committed by Ingo Molnar
parent 4dc88029fd
commit 392741e0a4
1 changed files with 9 additions and 2 deletions
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11
kernel/futex.c
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@ -1256,8 +1256,15 @@ retry_private:
if (!match_futex(&this->key, &key1))
continue;
WARN_ON(!requeue_pi && this->rt_waiter);
WARN_ON(requeue_pi && !this->rt_waiter);
/*
* FUTEX_WAIT_REQEUE_PI and FUTEX_CMP_REQUEUE_PI should always
* be paired with each other and no other futex ops.
*/
if ((requeue_pi && !this->rt_waiter) ||
(!requeue_pi && this->rt_waiter)) {
ret = -EINVAL;
break;
}
/*
* Wake nr_wake waiters. For requeue_pi, if we acquired the