linux-kernel - [PATCH v2][RESEND] cpuidle: Add checks to avoid NULL pointer dereference

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Date:	Mon, 30 Apr 2012 12:30:55 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	lenb@...nel.org, "Rafael J. Wysocki" <rjw@...k.pl>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
CC:	Daniel Lezcano <daniel.lezcano@...aro.org>, khilman@...com,
	Deepthi Dharwar <deepthi@...ux.vnet.ibm.com>,
	g.trinabh@...il.com, Arjan van de Ven <arjan@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux PM mailing list <linux-pm@...r.kernel.org>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Subject: [PATCH v2][RESEND] cpuidle: Add checks to avoid NULL pointer dereference

From: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>

The existing check for dev == NULL in __cpuidle_register_device() is rendered
useless because dev is dereferenced before the check itself. Moreover,
correctly speaking, it is the job of the callers of this function, i.e.,
cpuidle_register_device() & cpuidle_enable_device() (which also happen to be
exported functions) to ensure that __cpuidle_register_device() is called with
a non-NULL dev.

So add the necessary dev == NULL checks in the two callers and remove the
(useless) check from __cpuidle_register_device().

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
Acked-by: Daniel Lezcano <daniel.lezcano@...aro.org>
---

 drivers/cpuidle/cpuidle.c |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 87411ce..eae2f11 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -291,6 +291,9 @@ int cpuidle_enable_device(struct cpuidle_device *dev)
 	int ret, i;
 	struct cpuidle_driver *drv = cpuidle_get_driver();

+	if (!dev)
+		return -EINVAL;
+
 	if (dev->enabled)
 		return 0;
 	if (!drv || !cpuidle_curr_governor)
@@ -375,8 +378,6 @@ static int __cpuidle_register_device(struct cpuidle_device *dev)
 	struct device *cpu_dev = get_cpu_device((unsigned long)dev->cpu);
 	struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver();

-	if (!dev)
-		return -EINVAL;
 	if (!try_module_get(cpuidle_driver->owner))
 		return -EINVAL;

@@ -401,6 +402,9 @@ int cpuidle_register_device(struct cpuidle_device *dev)
 {
 	int ret;

+	if (!dev)
+		return -EINVAL;
+
 	mutex_lock(&cpuidle_lock);

 	if ((ret = __cpuidle_register_device(dev))) {


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