Re: [PATCH V3] cpuidle: check dev before usage in cpuidle_use_deepest_state

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

On Thursday, May 04, 2017 09:00:52 AM Li, Fei wrote:
> In case of there is no cpuidle devices registered, dev will be null, and 
> panic will be triggered like below;
> In this patch, add checking of dev before usage, like that done in
> cpuidle_idle_call.
> 
> Panic without fix:
> [  184.961328] BUG: unable to handle kernel NULL pointer dereference at
>   (null)
> [  184.961328] IP: cpuidle_use_deepest_state+0x30/0x60
> ...
> [  184.961328]  play_idle+0x8d/0x210
> [  184.961328]  ? __schedule+0x359/0x8e0
> [  184.961328]  ? _raw_spin_unlock_irqrestore+0x28/0x50
> [  184.961328]  ? kthread_queue_delayed_work+0x41/0x80
> [  184.961328]  clamp_idle_injection_func+0x64/0x1e0
> 
> Fixes: bb8313b603eb8 ("cpuidle: Allow enforcing deepest idle state selection")
> Signed-off-by: Li, Fei <fei.li@intel.com>
> Tested-by: Shi, Feng <fengx.shi@intel.com>
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Reviewed-by: Koul, Vinod <vinod.koul@intel.com>
> ---
>  drivers/cpuidle/cpuidle.c | 3 ++- 
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
> index 548b90b..2706be7 100644
> --- a/drivers/cpuidle/cpuidle.c
> +++ b/drivers/cpuidle/cpuidle.c
> @@ -111,7 +111,8 @@ void cpuidle_use_deepest_state(bool enable)
>  
>     preempt_disable();
>     dev = cpuidle_get_device();
> -   dev->use_deepest_state = enable;
> +   if (dev)
> +       dev->use_deepest_state = enable;
>     preempt_enable();
>  }
>  
> -- 
> 1.9.1

A previous version of this has been applied and I don't see any differences
in the code changes.

Thanks,
Rafael