linux-kernel - [PATCH 3.16 048/178] futex: Add missing error handling to FUTEX_REQUEUE

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Message-ID: <lsq.1500213406.818471263@decadent.org.uk>
Date:   Sun, 16 Jul 2017 14:56:46 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, bigeasy@...utronix.de,
        rostedt@...dmis.org, mathieu.desnoyers@...icios.com,
        bristot@...hat.com, "Peter Zijlstra" <peterz@...radead.org>,
        dvhart@...radead.org, jdesfossez@...icios.com, xlpang@...hat.com,
        juri.lelli@....com, "Darren Hart" <dvhart@...ux.intel.com>,
        "Thomas Gleixner" <tglx@...utronix.de>
Subject: [PATCH 3.16 048/178] futex: Add missing error handling to
 FUTEX_REQUEUE_PI

3.16.46-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Peter Zijlstra <peterz@...radead.org>

commit 9bbb25afeb182502ca4f2c4f3f88af0681b34cae upstream.

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
Link: http://lkml.kernel.org/r/20170304093558.867401760@infradead.org
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 kernel/futex.c | 2 ++
 1 file changed, 2 insertions(+)

--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2661,6 +2661,8 @@ static int futex_wait_requeue_pi(u32 __u
 		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.