[PATCH 3.4 014/134] intel_idle: Check cpu_idle_get_driver() for NULL before dereferencing it.

[Greg Kroah-Hartman]

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

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

From: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

commit 3735d524da64b70b41c764359da36f88aded3610 upstream.

If the machine is booted without any cpu_idle driver set
(b/c disable_cpuidle() has been called) we should follow
other users of cpu_idle API and check the return value
for NULL before using it.

Reported-and-tested-by: Mark van Dijk <mark@xxxxxxxxxxxxxx>
Suggested-by: Jan Beulich <JBeulich@xxxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
Cc: Daniel Kiper <daniel.kiper@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -594,8 +594,9 @@ static int __init intel_idle_init(void)
 	intel_idle_cpuidle_driver_init();
 	retval = cpuidle_register_driver(&intel_idle_driver);
 	if (retval) {
+		struct cpuidle_driver *drv = cpuidle_get_driver();
 		printk(KERN_DEBUG PREFIX "intel_idle yielding to %s",
-			cpuidle_get_driver()->name);
+			drv ? drv->name : "none");
 		return retval;
 	}
 


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