From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: [PATCH] cpuidle: Prevent null pointer dereference in cpuidle_coupled_cpu_notify Date: Wed, 15 Aug 2012 22:23:17 +0200 Message-ID: <201208152223.17623.rjw@sisk.pl> References: <1344945151.2674.56.camel@linaro1.home> Mime-Version: 1.0 Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1344945151.2674.56.camel@linaro1.home> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-pm-bounces@lists.linux-foundation.org Errors-To: linux-pm-bounces@lists.linux-foundation.org To: "Jon Medhurst (Tixy)" Cc: Len Brown , linux-kernel@vger.kernel.org, Colin Cross , linux-pm@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org List-Id: linux-pm@vger.kernel.org On Tuesday, August 14, 2012, Jon Medhurst (Tixy) wrote: > 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 Applied to the linux-next branch of the linux-pm.git tree as v3.6 material. Thanks, Rafael > --- > > 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) { >