2017-04-27 01:47:43

by Li Fei

Subject: [PATCH V2] cpuidle: check dev before usage in cpuidle_use_deepest_state

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 <[email protected]>
Tested-by: Shi, Feng <[email protected]>
---
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

Best Regards,
Fei

2017-04-27 09:41:11

by Andy Shevchenko

Subject: Re: [PATCH V2] cpuidle: check dev before usage in cpuidle_use_deepest_state

On Thu, 2017-04-27 at 01:47 +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

FWIW:
Reviewed-by: Andy Shevchenko <[email protected]>

P.S. V2 is mistakenly left from internal review AFAIU.

>
> Fixes: bb8313b603eb8 ("cpuidle: Allow enforcing deepest idle state
> selection")
> Signed-off-by: Li, Fei <[email protected]>
> Tested-by: Shi, Feng <[email protected]>
> ---
>  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();
>  }
>  

--
Andy Shevchenko <[email protected]>
Intel Finland Oy