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

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Date:   Fri, 5 Nov 2021 13:08:22 -0700
From:   Subbaraman Narayanamurthy <quic_subbaram@...cinc.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>
CC:     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 11/5/21 9:37 AM, Rafael J. Wysocki wrote:
> 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".

Thanks, Daniel and Rafael. So, I guess I don't need to send v3 with fixing commit subject right?

-Subbaraman