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Message-Id: <1454030348-17736-29-git-send-email-kamal@canonical.com>
Date: Thu, 28 Jan 2016 17:16:06 -0800
From: Kamal Mostafa <kamal@...onical.com>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org,
kernel-team@...ts.ubuntu.com
Cc: Thomas Gleixner <tglx@...utronix.de>,
Peter Zijlstra <peterz@...radead.org>,
Darren Hart <darren@...art.com>,
Davidlohr Bueso <dave@...olabs.net>,
Bhuvanesh_Surachari@...tor.com, Andy Lowe <Andy_Lowe@...tor.com>,
Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 028/210] futex: Drop refcount if requeue_pi() acquired the rtmutex
3.19.8-ckt14 -stable review patch. If anyone has any objections, please let me know.
---8<------------------------------------------------------------
From: Thomas Gleixner <tglx@...utronix.de>
commit fb75a4282d0d9a3c7c44d940582c2d226cf3acfb upstream.
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@...utronix.de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Darren Hart <darren@...art.com>
Cc: Davidlohr Bueso <dave@...olabs.net>
Cc: Bhuvanesh_Surachari@...tor.com
Cc: Andy Lowe <Andy_Lowe@...tor.com>
Link: http://lkml.kernel.org/r/20151219200607.178132067@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
kernel/futex.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/kernel/futex.c b/kernel/futex.c
index 63678b5..1c43013 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2632,6 +2632,11 @@ 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);
+ /*
+ * 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 {
--
1.9.1
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