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>
(cherry picked from commit 13c42c2f43b19aab3195f2d357db00d1e885eaa8)
[wt: 2.6.32 needs &q as first argument of queue_unlock()]
Signed-off-by: Willy Tarreau <w@1wt.eu>

diff --git a/kernel/futex.c b/kernel/futex.c
index 55dd3d21f4c1f5d1db5ed9bff6863500fa34b8b8..1e092d3465c164731684cc78be4f794f0b49f203 100644 (file)
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2414,6 +2414,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, int fshared,
         * shared futexes. We need to compare the keys:
         */
        if (match_futex(&q.key, &key2)) {
+               queue_unlock(&q, hb);
                ret = -EINVAL;
                goto out_put_keys;
        }