[3.11.y.z extended stable] Patch "cpuidle: Check the result of cpuidle_get_driver() against NULL" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    cpuidle: Check the result of cpuidle_get_driver() against NULL

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 77092523a3e51fd593d04bcfe72ac19ca8deb6ae Mon Sep 17 00:00:00 2001
From: Daniel Fu <danifu at nvidia.com>
Date: Fri, 30 Aug 2013 19:48:22 +0800
Subject: cpuidle: Check the result of cpuidle_get_driver() against NULL

commit 3b9c10e98021e1f92e6f8c7ce1778b86ba68db10 upstream.

If the current CPU has no cpuidle driver, drv will be NULL in
cpuidle_driver_ref().  Check if that is the case before trying
to bump up the driver's refcount to prevent the kernel from
crashing.

[rjw: Subject and changelog]
Signed-off-by: Daniel Fu <danifu at nvidia.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
Cc: Mark Brown <broonie at kernel.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/cpuidle/driver.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/cpuidle/driver.c b/drivers/cpuidle/driver.c
index 3ac499d..6e11701 100644
--- a/drivers/cpuidle/driver.c
+++ b/drivers/cpuidle/driver.c
@@ -331,7 +331,8 @@ struct cpuidle_driver *cpuidle_driver_ref(void)
 	spin_lock(&cpuidle_driver_lock);

 	drv = cpuidle_get_driver();
-	drv->refcnt++;
+	if (drv)
+		drv->refcnt++;

 	spin_unlock(&cpuidle_driver_lock);
 	return drv;
--
1.9.1