From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Jon Medhurst (Tixy)" Subject: [PATCH] cpuidle: Prevent null pointer dereference in cpuidle_coupled_cpu_notify Date: Tue, 14 Aug 2012 12:52:31 +0100 Message-ID: <1344945151.2674.56.camel@linaro1.home> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: linux-kernel@vger.kernel.org Cc: "Rafael J. Wysocki" , Len Brown , linux-pm@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org, Colin Cross List-Id: linux-pm@vger.kernel.org When a kernel is built to support multiple hardware types it's possible that CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED is set but the hardware the kernel is run on doesn't support cpuidle and therefore doesn't load a driver for it. In this case, when the system is shut down, cpuidle_coupled_cpu_notify() gets called with cpuidle_devices set to NULL. There are quite possibly other circumstances where this situation can also occur and we should check for it. Signed-off-by: Jon Medhurst --- Would a better fix be to delay registering the notifier until cpuidle_coupled_register_device() is called? Though following through with that logic would require unregistering the notifier when cpuidle driver is unregistered and it still seems possible that there would still be a window of opportunity for things to go wrong. drivers/cpuidle/coupled.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/cpuidle/coupled.c b/drivers/cpuidle/coupled.c index 2c9bf26..c78a5ff 100644 --- a/drivers/cpuidle/coupled.c +++ b/drivers/cpuidle/coupled.c @@ -681,7 +681,7 @@ static int cpuidle_coupled_cpu_notify(struct notifier_block *nb, mutex_lock(&cpuidle_lock); dev = per_cpu(cpuidle_devices, cpu); - if (!dev->coupled) + if (!dev || !dev->coupled) goto out; switch (action & ~CPU_TASKS_FROZEN) { -- 1.7.10.4