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    Subject[PATCH 3.13 061/163] futex: Unlock hb->lock in futex_wait_requeue_pi() error path
    Date
    3.13.11.9 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Thomas Gleixner <tglx@linutronix.de>

    commit 13c42c2f43b19aab3195f2d357db00d1e885eaa8 upstream.

    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>
    Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1409112318500.4178@nanos
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    [ kamal: backport to 3.13-stable: queue_unlock() args ]
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    kernel/futex.c | 1 +
    1 file changed, 1 insertion(+)

    diff --git a/kernel/futex.c b/kernel/futex.c
    index c265aac..4741b1f 100644
    --- a/kernel/futex.c
    +++ b/kernel/futex.c
    @@ -2465,6 +2465,7 @@ 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(&q, hb);
    ret = -EINVAL;
    goto out_put_keys;
    }
    --
    1.9.1


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