linux-kernel - [tip:locking/urgent] futex: Add missing error handling to FUTEX_REQUEUE

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Date:   Tue, 14 Mar 2017 13:49:24 -0700
From:   tip-bot for Peter Zijlstra <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     mingo@...nel.org, hpa@...or.com, peterz@...radead.org,
        tglx@...utronix.de, dvhart@...ux.intel.com,
        linux-kernel@...r.kernel.org
Subject: [tip:locking/urgent] futex: Add missing error handling to
 FUTEX_REQUEUE_PI

Commit-ID:  9bbb25afeb182502ca4f2c4f3f88af0681b34cae
Gitweb:     http://git.kernel.org/tip/9bbb25afeb182502ca4f2c4f3f88af0681b34cae
Author:     Peter Zijlstra <peterz@...radead.org>
AuthorDate: Sat, 4 Mar 2017 10:27:19 +0100
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Tue, 14 Mar 2017 21:45:36 +0100

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@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Darren Hart <dvhart@...ux.intel.com>
Cc: juri.lelli@....com
Cc: bigeasy@...utronix.de
Cc: xlpang@...hat.com
Cc: rostedt@...dmis.org
Cc: mathieu.desnoyers@...icios.com
Cc: jdesfossez@...icios.com
Cc: dvhart@...radead.org
Cc: bristot@...hat.com
Cc: stable@...r.kernel.org
Link: http://lkml.kernel.org/r/20170304093558.867401760@infradead.org
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

---
 kernel/futex.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/futex.c b/kernel/futex.c
index 3a4775f..45858ec 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.