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In-Reply-To: <fa69384f-1485-142b-c4ee-3df54ac68a89@web.de>
From:   Robert Foss <rfoss@kernel.org>
Date:   Fri, 28 Apr 2023 19:27:54 +0200
Message-ID: <CAN6tsi5vukABCxWMNtUHokXj3+xObnX_aKvP-oQDde+M+Biv4g@mail.gmail.com>
Subject: Re: [PATCH resent] drm/bridge: it6505: Move a variable assignment
 behind a null pointer check in receive_timing_debugfs_show()
To:     Markus Elfring <Markus.Elfring@web.de>
Cc:     kernel-janitors@vger.kernel.org, dri-devel@lists.freedesktop.org,
        Andrzej Hajda <andrzej.hajda@intel.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        David Airlie <airlied@gmail.com>,
        Hermes Wu <hermes.wu@ite.com.tw>,
        Hsin-yi Wang <hsinyi@chromium.org>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Jonas Karlman <jonas@kwiboo.se>,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        Neil Armstrong <neil.armstrong@linaro.org>,
        LKML <linux-kernel@vger.kernel.org>, cocci@inria.fr
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On Fri, Apr 28, 2023 at 5:56=E2=80=AFPM Markus Elfring <Markus.Elfring@web.=
de> wrote:
>
> From: Markus Elfring <elfring@users.sourceforge.net>
> Date: Sun, 16 Apr 2023 17:30:46 +0200
>
> The address of a data structure member was determined before
> a corresponding null pointer check in the implementation of
> the function =E2=80=9Creceive_timing_debugfs_show=E2=80=9D.
>
> Thus avoid the risk for undefined behaviour by moving the assignment
> for the variable =E2=80=9Cvid=E2=80=9D behind the null pointer check.
>
> This issue was detected by using the Coccinelle software.
>
> Fixes: b5c84a9edcd418cd055becad6a22439e7c5e3bf8 ("drm/bridge: add it6505 =
driver")
> Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
> ---
>  drivers/gpu/drm/bridge/ite-it6505.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/bridge/ite-it6505.c b/drivers/gpu/drm/bridge=
/ite-it6505.c
> index abaf6e23775e..45f579c365e7 100644
> --- a/drivers/gpu/drm/bridge/ite-it6505.c
> +++ b/drivers/gpu/drm/bridge/ite-it6505.c
> @@ -3207,7 +3207,7 @@ static ssize_t receive_timing_debugfs_show(struct f=
ile *file, char __user *buf,
>                                            size_t len, loff_t *ppos)
>  {
>         struct it6505 *it6505 =3D file->private_data;
> -       struct drm_display_mode *vid =3D &it6505->video_info;
> +       struct drm_display_mode *vid;
>         u8 read_buf[READ_BUFFER_SIZE];
>         u8 *str =3D read_buf, *end =3D read_buf + READ_BUFFER_SIZE;
>         ssize_t ret, count;
> @@ -3216,6 +3216,7 @@ static ssize_t receive_timing_debugfs_show(struct f=
ile *file, char __user *buf,
>                 return -ENODEV;
>
>         it6505_calc_video_info(it6505);
> +       vid =3D &it6505->video_info;
>         str +=3D scnprintf(str, end - str, "---video timing---\n");
>         str +=3D scnprintf(str, end - str, "PCLK:%d.%03dMHz\n",
>                          vid->clock / 1000, vid->clock % 1000);
> --
> 2.40.0
>

Applied to drm-misc-next.