Re: [PATCH -next] thermal/drivers/thermal_hwmon: Fix a kernel NULL pointer dereference

[Daniel Lezcano]

On 29/03/2023 18:03, Rafael J. Wysocki wrote:
> On Wed, Mar 29, 2023 at 5:59 PM Daniel Lezcano
> <daniel.lezcano@xxxxxxxxxx> wrote:
> > On 29/03/2023 16:38, Rafael J. Wysocki wrote:
> > > On Wed, Mar 29, 2023 at 4:16 PM Daniel Lezcano
> > > <daniel.lezcano@xxxxxxxxxx> wrote:
> > > > On 29/03/2023 14:06, Rafael J. Wysocki wrote:
> > > > > On Wed, Mar 29, 2023 at 11:57 AM Daniel Lezcano
> > > > > <daniel.lezcano@xxxxxxxxxx> wrote:
> > > > > > On 29/03/2023 11:00, Zhang Rui wrote:
> > > > > > > When the hwmon device node of a thermal zone device is not found,
> > > > > > > using hwmon->device causes a kernel NULL pointer dereference.
> > > > > > >
> > > > > > > Reported-by: Preble Adam C <adam.c.preble@xxxxxxxxx>
> > > > > > > Signed-off-by: Zhang Rui <rui.zhang@xxxxxxxxx>
> > > > > > > ---
> > > > > > > Fixes: dec07d399cc8 ("thermal: Don't use 'device' internal thermal zone structure field")
> > > > > > > dec07d399cc8 is a commit in the linux-next branch of linux-pm repo.
> > > > > > > I'm not sure if the Fix tag applies to such commit or not.
> > > > > >
> > > > > > Actually it reverts the work done to encapsulate the thermal zone device
> > > > > > structure.
> > > > >
> > > > > So maybe instead of the wholesale switch to using "driver-specific"
> > > > > device pointers for printing messages, something like
> > > > > thermal_zone_debug/info/warn/error() taking a thermal zone pointer as
> > > > > the first argument can be defined?
> > > > >
> > > > > At least this particular bug could be avoided this way.
> > > >
> > > > Actually we previously said the thermal_hwmon can be considered as part
> > > > of the thermal core code, so we can keep using tz->device.
> > > >
> > > > I'll drop this change from the series.
> > >
> > > But it's there in my thermal branch already.
> > >
> > > Do you want to revert the thermal_hwmon.c part of commit dec07d399cc8?
> >
> > Oh, right. Fair enough.
> >
> > I think Rui's patch is fine then.
>
> I guess you mean the $subject one, that is:
>
> https://patchwork.kernel.org/project/linux-pm/patch/20230329090055.7537-1-rui.zhang@xxxxxxxxx

Correct

> What about the message printed when temp is NULL.  Should the original
> form of it be restored too?

Yes, you are right, for the sake of consistency we should restore also 
this one.



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