Commit 13c42c2f authored Sep 11, 2014 by Thomas Gleixner

futex: Unlock hb->lock in futex_wait_requeue_pi() error path



futex_wait_requeue_pi() calls futex_wait_setup(). If
futex_wait_setup() succeeds it returns with hb->lock held and
preemption disabled. Now the sanity check after this does:

        if (match_futex(&q.key, &key2)) {
	   	ret = -EINVAL;
		goto out_put_keys;
	}

which releases the keys but does not release hb->lock.

So we happily return to user space with hb->lock held and therefor
preemption disabled.

Unlock hb->lock before taking the exit route.

Reported-by: Dave "Trinity" Jones <davej@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Darren Hart <dvhart@linux.intel.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1409112318500.4178@nanos


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

parent 471cff7c

kernel/futex.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -2592,6 +2592,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
		* shared futexes. We need to compare the keys:
		*/
		if (match_futex(&q.key, &key2)) {
		queue_unlock(hb);
		ret = -EINVAL;
		goto out_put_keys;
		}

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