[PATCH 3.10 06/41] cpuidle: Check the result of cpuidle_get_driver() against NULL

[Greg Kroah-Hartman]

3.10-stable review patch.  If anyone has any objections, please let me know.

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

From: Daniel Fu <danifu@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Cc: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/cpuidle/driver.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/cpuidle/driver.c
+++ b/drivers/cpuidle/driver.c
@@ -251,7 +251,8 @@ struct cpuidle_driver *cpuidle_driver_re
 	spin_lock(&cpuidle_driver_lock);
 
 	drv = cpuidle_get_driver();
-	drv->refcnt++;
+	if (drv)
+		drv->refcnt++;
 
 	spin_unlock(&cpuidle_driver_lock);
 	return drv;


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