[patch 1/5] futex: Drop refcount if requeue_pi() acquired the rtmutex

From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Darren Hart <darren@dvhart.com>,
	Davidlohr Bueso <dave@stgolabs.net>,
	Bhuvanesh_Surachari@mentor.com, Andy Lowe <Andy_Lowe@mentor.com>
Subject: [patch 1/5] futex: Drop refcount if requeue_pi() acquired the rtmutex
Date: Sat, 19 Dec 2015 20:07:38 -0000	[thread overview]
Message-ID: <20151219200607.178132067@linutronix.de> (raw)
In-Reply-To: 20151219200501.563704646@linutronix.de

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If the proxy lock in the requeue loop acquires the rtmutex for a
waiter then it acquired also refcount on the pi_state related to the
futex, but the waiter side does not drop the reference count.

Add the missing free_pi_state() call.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
---
 kernel/futex.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2755,6 +2755,11 @@ 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);
+			/*
+			 * Drop the reference to the pi state which
+			 * the requeue_pi() code acquired for us.
+			 */
+			free_pi_state(q.pi_state);
 			spin_unlock(q.lock_ptr);
 		}
 	} else {


