On Thu, May 04, 2017 at 09:00:52AM +0000, 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...@intel.com>
> Tested-by: Shi, Feng <fengx....@intel.com>
> Reviewed-by: Andy Shevchenko <andriy.shevche...@linux.intel.com>
> Reviewed-by: Koul, Vinod <vinod.k...@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;
This change is acceptable as a hot fix but the question is 'why is this
function called if there is no cpuidle driver registered?'
> preempt_enable();
> }
>
> --
> 1.9.1
>
> Best Regards,
> Fei
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