[v1] Fix some errors in the devfreq core layer when governor is NULL

[PATCH RESEND 0/4] Fix some errors in the devfreq core layer when governor is NULL

Posted by Yaxiong Tian 2 weeks, 4 days ago

While doing some development work with devfreq_add_governor()/
devfreq_remove_governor(), I discovered several bugs caused when
devfreq->governor is NULL. Specifically:

1) A possible null pointer issue in devfreq_add_governor(), caused
by devfreq_remove_governor() setting devfreq->governor to NULL in
certain situations, while devfreq_add_governor() lacks corresponding
checks for devfreq->governor.

2) When operating on governor and available_governors under /sys,
there are also some unexpected errors.

See the following patches for details.

Yaxiong Tian (4):
  PM / devfreq: Fix possible null pointer issue in
    devfreq_add_governor()
  PM / devfreq: Fix available_governors_show() when no governor is set
  PM / devfreq: Fix governor_store() failing when device has no current
    governor
  PM / devfreq: Optimize error return value of governor_show()

 drivers/devfreq/devfreq.c | 46 +++++++++++++++++++++------------------
 1 file changed, 25 insertions(+), 21 deletions(-)

-- 
2.25.1

Re: [PATCH RESEND 0/4] Fix some errors in the devfreq core layer when governor is NULL

Posted by Jie Zhan 1 week, 5 days ago


On 3/19/2026 5:14 PM, Yaxiong Tian wrote:
> While doing some development work with devfreq_add_governor()/
> devfreq_remove_governor(), I discovered several bugs caused when
> devfreq->governor is NULL. Specifically:
> 
> 1) A possible null pointer issue in devfreq_add_governor(), caused
> by devfreq_remove_governor() setting devfreq->governor to NULL in
> certain situations, while devfreq_add_governor() lacks corresponding
> checks for devfreq->governor.
> 
> 2) When operating on governor and available_governors under /sys,
> there are also some unexpected errors.
> 
> See the following patches for details.
Hi Yaxiong,

Sorry for catching this late.

I happen to be working on the same issues recently on a local tree, though
delayed for quite a while due to other business.

It would be a totally different approach by reworking the locking logic,
which, I supposed, can make the devfreq framework cleaner to maintain.

I'll send it out shortly.  Hopefully it can be a reference for us to
discuss with.

Thanks!
Jie
> 
> Yaxiong Tian (4):
>   PM / devfreq: Fix possible null pointer issue in
>     devfreq_add_governor()
>   PM / devfreq: Fix available_governors_show() when no governor is set
>   PM / devfreq: Fix governor_store() failing when device has no current
>     governor
>   PM / devfreq: Optimize error return value of governor_show()
> 
>  drivers/devfreq/devfreq.c | 46 +++++++++++++++++++++------------------
>  1 file changed, 25 insertions(+), 21 deletions(-)
>