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

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Date:   Wed, 29 Mar 2023 12:33:36 +0000
From:   "Zhang, Rui" <rui.zhang@...el.com>
To:     "rafael@...nel.org" <rafael@...nel.org>,
        "daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>
CC:     "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -next] thermal/drivers/thermal_hwmon: Fix a kernel NULL
 pointer dereference

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@...aro.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@...el.com>
> > > Signed-off-by: Zhang Rui <rui.zhang@...el.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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