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

Rafael J. Wysocki
2023-03-29T10:56:04Z

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.
>
> > ---
> > 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;
>

Or just use pr_debug() instead of dev_dbg().

>
> > return;
> > }
> >