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

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Message-ID: <CAJZ5v0gONybD_pVCAq6ZJTMuStXtoF064u9qPYxco4y=b-JD9A@mail.gmail.com>
Date:   Fri, 5 Nov 2021 16:14:56 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Subbaraman Narayanamurthy <quic_subbaram@...cinc.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     "Rafael J . Wysocki" <rafael@...nel.org>,
        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 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?

> ---
>  drivers/thermal/thermal_of.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/thermal/thermal_of.c b/drivers/thermal/thermal_of.c
> index 6379f26..9233f7e 100644
> --- a/drivers/thermal/thermal_of.c
> +++ b/drivers/thermal/thermal_of.c
> @@ -89,7 +89,7 @@ static int of_thermal_get_temp(struct thermal_zone_device *tz,
>  {
>         struct __thermal_zone *data = tz->devdata;
>
> -       if (!data->ops->get_temp)
> +       if (!data->ops || !data->ops->get_temp)
>                 return -EINVAL;
>
>         return data->ops->get_temp(data->sensor_data, temp);
> @@ -186,6 +186,9 @@ static int of_thermal_set_emul_temp(struct thermal_zone_device *tz,
>  {
>         struct __thermal_zone *data = tz->devdata;
>
> +       if (!data->ops || !data->ops->set_emul_temp)
> +               return -EINVAL;
> +
>         return data->ops->set_emul_temp(data->sensor_data, temp);
>  }
>
> @@ -194,7 +197,7 @@ static int of_thermal_get_trend(struct thermal_zone_device *tz, int trip,
>  {
>         struct __thermal_zone *data = tz->devdata;
>
> -       if (!data->ops->get_trend)
> +       if (!data->ops || !data->ops->get_trend)
>                 return -EINVAL;
>
>         return data->ops->get_trend(data->sensor_data, trip, trend);
> @@ -301,7 +304,7 @@ static int of_thermal_set_trip_temp(struct thermal_zone_device *tz, int trip,
>         if (trip >= data->ntrips || trip < 0)
>                 return -EDOM;
>
> -       if (data->ops->set_trip_temp) {
> +       if (data->ops && data->ops->set_trip_temp) {
>                 int ret;
>
>                 ret = data->ops->set_trip_temp(data->sensor_data, trip, temp);
> --
> 2.7.4
>