Re: [PATCH] cpuidle: Prevent null pointer dereference in cpuidle_coupled_cpu_notify
From: Rafael J. Wysocki <hidden>
Date: 2012-08-15 20:17:47
Also in:
linux-arm-kernel, lkml
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 <redacted>
Applied to the linux-next branch of the linux-pm.git tree as v3.6 material. Thanks, Rafael
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--- 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) {