[PATCH 13/52] cpuidle: add checks to avoid NULL pointer dereference

Len Brown
2012-07-25T03:42:30Z

From: "Srivatsa S. Bhat" <srivatsa.bhat@linux.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@linux.vnet.ibm.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>
---
drivers/cpuidle/cpuidle.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 588b44a..8ffef26 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -285,6 +285,9 @@ 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)
@@ -369,8 +372,6 @@ 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;

@@ -395,6 +396,9 @@ int cpuidle_register_device(struct cpuidle_device *dev)
{
int ret;

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

if ((ret = __cpuidle_register_device(dev))) {
--
1.7.12.rc0