linux-kernel - Re: [PATCH] drm/bridge: ps8640: Return NULL immediately when EDID read fail

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Message-ID: <CAN6tsi7M26ijWT0hVOAoSFE6fhy-0TS-c7+5LUJpo-NJAG21Mw@mail.gmail.com>
Date:   Fri, 24 Mar 2023 15:05:22 +0100
From:   Robert Foss <rfoss@...nel.org>
To:     Pin-yen Lin <treapking@...omium.org>
Cc:     Douglas Anderson <dianders@...omium.org>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/bridge: ps8640: Return NULL immediately when EDID
 read fail

On Fri, Mar 24, 2023 at 4:59 AM Pin-yen Lin <treapking@...omium.org> wrote:
>
> drm_edid_read returns NULL on error, so feeding it directly into
> drm_edid_duplicate may lead to NULL pointer dereference. Add a check to
> guard this.
>
> Fixes: 6a17b4d1b52f ("drm/bridge: ps8640: Add a cache for EDID")
> Signed-off-by: Pin-yen Lin <treapking@...omium.org>
> ---
>
>  drivers/gpu/drm/bridge/parade-ps8640.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
> index cddbfe91f75e..b823e55650b1 100644
> --- a/drivers/gpu/drm/bridge/parade-ps8640.c
> +++ b/drivers/gpu/drm/bridge/parade-ps8640.c
> @@ -543,6 +543,7 @@ static struct edid *ps8640_bridge_get_edid(struct drm_bridge *bridge,
>                                            struct drm_connector *connector)
>  {
>         struct ps8640 *ps_bridge = bridge_to_ps8640(bridge);
> +       struct device *dev = &ps_bridge->page[PAGE0_DP_CNTL]->dev;
>         bool poweroff = !ps_bridge->pre_enabled;
>
>         if (!ps_bridge->edid) {
> @@ -574,6 +575,11 @@ static struct edid *ps8640_bridge_get_edid(struct drm_bridge *bridge,
>                                                              connector->state->state);
>         }
>
> +       if (!ps_bridge->edid) {
> +               dev_err(dev, "Failed to get EDID\n");
> +               return NULL;
> +       }
> +
>         return drm_edid_duplicate(ps_bridge->edid);
>  }
>
> --
> 2.40.0.348.gf938b09366-goog
>

Reviewed-by: Robert Foss <rfoss@...nel.org>