| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.16 245/357] futex: Unlock hb->lock in futex_wait_requeue_pi() error path | Date | Fri, 3 Oct 2014 14:30:31 -0700 |
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3.16-stable review patch. If anyone has any objections, please let me know.
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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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- kernel/futex.c | 1 + 1 file changed, 1 insertion(+)
--- a/kernel/futex.c +++ b/kernel/futex.c @@ -2628,6 +2628,7 @@ static int futex_wait_requeue_pi(u32 __u * 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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