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

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

[Li, Fei]

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

Best Regards,
Fei

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

[Daniel Lezcano]

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.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;


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

[Li, Fei]

On Thursday, May 4, 2017 6:16 PM Daniel Lezcano wrote:
> >
> >     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?'

It's called as below:
clamp_idle_injection_func
	-> play_idle
		-> cpuidle_use_deepest_state
In play_idle, if no cpuidle driver registered, cpu_idle_poll can be called.
It seems to go too far if not calling play_idle in case of no cpuidle driver
registered.
At present no other suitable and simple fix seen.

> 
> >     preempt_enable();
> >  }
> >
> > --
> > 1.9.1
> >
> > Best Regards,
> > Fei
> 
> --
> 
>  <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs
> 
> Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
> <http://twitter.com/#!/linaroorg> Twitter |
> <http://www.linaro.org/linaro-blog/> Blog

Best Regards,
Fei

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

[Rafael J. Wysocki]

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

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

[Andy Shevchenko]

On Sat, May 6, 2017 at 12:33 AM, Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
> On Thursday, May 04, 2017 09:00:52 AM Li, Fei wrote:

>> 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>

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

AFAIR only tags (above) had been extended in v3.

-- 
With Best Regards,
Andy Shevchenko

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

[Li, Fei]

> >> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> >> Reviewed-by: Koul, Vinod <vinod.koul@intel.com>
> 
> > A previous version of this has been applied and I don't see any differences
> > in the code changes.
> 
> AFAIR only tags (above) had been extended in v3.

Thanks.
Yes, for v3 no change in code, and only tags "Reviewed-by" added.

> 
> --
> With Best Regards,
> Andy Shevchenko

Best Regards,
Fei