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

Zhang, Rui
2023-03-29T12:33:53Z

On Wed, 2023-03-29 at 14:06 +0200, Rafael J. Wysocki wrote:
> On Wed, Mar 29, 2023 at 11:57 AM Daniel Lezcano
> <daniel.lezcano@linaro.org> 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@intel.com>
> > > Signed-off-by: Zhang Rui <rui.zhang@intel.com>
> > > ---
> > > 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.

I didn't see your email before sending patch v2.

are we going to rework the previous series from Daniel thus patch v2 is
no longer needed?

thanks,
rui
>
> > > ---
> > > drivers/thermal/thermal_hwmon.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/thermal/thermal_hwmon.c
> > > b/drivers/thermal/thermal_hwmon.c
> > > index c59db17dddd6..261743f461be 100644
> > > --- a/drivers/thermal/thermal_hwmon.c
> > > +++ b/drivers/thermal/thermal_hwmon.c
> > > @@ -229,7 +229,7 @@ void thermal_remove_hwmon_sysfs(struct
> > > thermal_zone_device *tz)
> > > hwmon = thermal_hwmon_lookup_by_type(tz);
> > > if (unlikely(!hwmon)) {
> > > /* Should never happen... */
> > > - dev_dbg(hwmon->device, "hwmon device lookup
> > > failed!\n");
> > > + dev_dbg(&tz->device, "hwmon device lookup
> > > failed!\n");
> >
> > As it 'Should never happen', I would replace that by:
> >
> > if (WARN_ON(!hwmon))
> > /* Should never happen... */
> > return;
> >
> >
> >
> > > return;
> > > }
> > >
> >
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