linux-kernel - Re: [RESEND PATCH v2] thermal: Fix a NULL pointer dereference

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Date:   Fri, 5 Nov 2021 17:37:33 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Subbaraman Narayanamurthy <quic_subbaram@...cinc.com>,
        Amit Kucheria <amitk@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        David Collins <quic_collinsd@...cinc.com>,
        Manaf Meethalavalappu Pallikunhi <quic_manafm@...cinc.com>,
        Stable <stable@...r.kernel.org>
Subject: Re: [RESEND PATCH v2] thermal: Fix a NULL pointer dereference

On Fri, Nov 5, 2021 at 5:19 PM Daniel Lezcano <daniel.lezcano@...aro.org> wrote:
>
> On 05/11/2021 16:14, Rafael J. Wysocki wrote:
> > On Fri, Nov 5, 2021 at 12:57 AM Subbaraman Narayanamurthy
> > <quic_subbaram@...cinc.com> wrote:
> >>
> >> of_parse_thermal_zones() parses the thermal-zones node and registers a
> >> thermal_zone device for each subnode. However, if a thermal zone is
> >> consuming a thermal sensor and that thermal sensor device hasn't probed
> >> yet, an attempt to set trip_point_*_temp for that thermal zone device
> >> can cause a NULL pointer dereference. Fix it.
> >>
> >>  console:/sys/class/thermal/thermal_zone87 # echo 120000 > trip_point_0_temp
> >>  ...
> >>  Unable to handle kernel NULL pointer dereference at virtual address 0000000000000020
> >>  ...
> >>  Call trace:
> >>   of_thermal_set_trip_temp+0x40/0xc4
> >>   trip_point_temp_store+0xc0/0x1dc
> >>   dev_attr_store+0x38/0x88
> >>   sysfs_kf_write+0x64/0xc0
> >>   kernfs_fop_write_iter+0x108/0x1d0
> >>   vfs_write+0x2f4/0x368
> >>   ksys_write+0x7c/0xec
> >>   __arm64_sys_write+0x20/0x30
> >>   el0_svc_common.llvm.7279915941325364641+0xbc/0x1bc
> >>   do_el0_svc+0x28/0xa0
> >>   el0_svc+0x14/0x24
> >>   el0_sync_handler+0x88/0xec
> >>   el0_sync+0x1c0/0x200
> >>
> >> While at it, fix the possible NULL pointer dereference in other
> >> functions as well: of_thermal_get_temp(), of_thermal_set_emul_temp(),
> >> of_thermal_get_trend().
> >
> > Can the subject be more specific, please?
> >
> > The issue appears to be limited to the of_thermal_ family of
> > functions, but the subject doesn't reflect that at all.
> >
> >> Suggested-by: David Collins <quic_collinsd@...cinc.com>
> >> Signed-off-by: Subbaraman Narayanamurthy <quic_subbaram@...cinc.com>
> >
> > Daniel, any concerns regarding the code changes below?
>
> I've a concern about the root cause but I did not have time to
> investigate how to fix it nicely.
>
> thermal_of is responsible of introducing itself between the thermal core
> code and the backend. So it defines the ops which in turn call the
> sensor ops leading us to this problem.
>
> So, without a better solution, this fix can be applied until we rethink
> the thermal_of approach.
>
> Acked-by: Daniel Lezcano <daniel.lezcano@...aro.org>

Thanks!

I've queued it up for 5.16-rc as "thermal: Fix NULL pointer
dereferences in of_thermal_ functions".