linux-kernel - [PATCH 3.2 200/200] intel_idle: Check cpu_idle_get_driver() for NULL before dereferencing it.

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Message-ID: <lsq.1396221815.285196957@decadent.org.uk>
Date:	Mon, 31 Mar 2014 00:23:35 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Jan Beulich" <JBeulich@...e.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	"Konrad Rzeszutek Wilk" <konrad.wilk@...cle.com>
Subject: [PATCH 3.2 200/200] intel_idle: Check cpu_idle_get_driver() for
 NULL before dereferencing it.

3.2.56-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>

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@...ernecto.net>
Suggested-by: Jan Beulich <JBeulich@...e.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 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
@@ -584,8 +584,9 @@ 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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