futex: Add missing error handling to FUTEX_REQUEUE_PI

Thomas spotted that fixup_pi_state_owner() can return errors and we
fail to unlock the rt_mutex in that case.

Reported-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Darren Hart <dvhart@linux.intel.com>
Cc: juri.lelli@arm.com
Cc: bigeasy@linutronix.de
Cc: xlpang@redhat.com
Cc: rostedt@goodmis.org
Cc: mathieu.desnoyers@efficios.com
Cc: jdesfossez@efficios.com
Cc: dvhart@infradead.org
Cc: bristot@redhat.com
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20170304093558.867401760@infradead.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 2 insertions, 0 deletions

diff --git a/kernel/futex.c b/kernel/futex.c
index 3a4775fd7468..45858ec73941 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2898,6 +2898,8 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
                 if (q.pi_state && (q.pi_state->owner != current)) {
                         spin_lock(q.lock_ptr);
                         ret = fixup_pi_state_owner(uaddr2, &q, current);
+                        if (ret && rt_mutex_owner(&q.pi_state->pi_mutex) == current)
+                                rt_mutex_unlock(&q.pi_state->pi_mutex);
                         /*
                          * Drop the reference to the pi state which
                          * the requeue_pi() code acquired for us.