linux-kernel - [PATCH 1/4] rtmutex: avoid null derefence in WARN

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Date:	Fri,  9 Jul 2010 15:32:57 -0700
From:	Darren Hart <dvhltc@...ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Eric Dumazet <eric.dumazet@...il.com>,
	John Kacur <jkacur@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mike Galbraith <efault@....de>, linux-rt-users@...r.kernel.org,
	Darren Hart <dvhltc@...ibm.com>
Subject: [PATCH 1/4] rtmutex: avoid null derefence in WARN_ON

If the pi_blocked_on variable is NULL, the subsequent WARN_ON's
will cause an OOPS. Only perform the susequent checks if
pi_blocked_on is valid.

Signed-off-by: Darren Hart <dvhltc@...ibm.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Eric Dumazet <eric.dumazet@...il.com>
Cc: John Kacur <jkacur@...hat.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Mike Galbraith <efault@....de>
---
 kernel/rtmutex.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
index 23dd443..baac7d9 100644
--- a/kernel/rtmutex.c
+++ b/kernel/rtmutex.c
@@ -579,9 +579,10 @@ static void wakeup_next_waiter(struct rt_mutex *lock, int savestate)
 
 	raw_spin_lock(&pendowner->pi_lock);
 
-	WARN_ON(!pendowner->pi_blocked_on);
-	WARN_ON(pendowner->pi_blocked_on != waiter);
-	WARN_ON(pendowner->pi_blocked_on->lock != lock);
+	if (!WARN_ON(!pendowner->pi_blocked_on)) {
+		WARN_ON(pendowner->pi_blocked_on != waiter);
+		WARN_ON(pendowner->pi_blocked_on->lock != lock);
+	}
 
 	pendowner->pi_blocked_on = NULL;
 
-- 
1.7.0.4

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