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

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Date:   Wed, 29 Mar 2023 15:50:27 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     "Zhang, Rui" <rui.zhang@...el.com>
Cc:     "rafael@...nel.org" <rafael@...nel.org>,
        "daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
        "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, Mar 29, 2023 at 2:33 PM Zhang, Rui <rui.zhang@...el.com> wrote:
>
> 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?

Well, let's see what Daniel says..

In any case, though, it is not very useful to carry an obvious NULL
pointer dereference in linux-next and the pr_debug() statement added
by the v2 can be replaced later, so I think I'll apply it.