linux-kernel - Re: [PATCH 1/3] drm/bridge: imx8qxp-ldb: Fix NULL pointer dereference in imx8qxp_ldb_bridge

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Message-ID: <aXOL8K/aiIQkU1Xu@lizhi-Precision-Tower-5810>
Date: Fri, 23 Jan 2026 09:55:44 -0500
From: Frank Li <Frank.li@....com>
To: Liu Ying <victor.liu@....com>
Cc: Andrzej Hajda <andrzej.hajda@...el.com>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	Robert Foss <rfoss@...nel.org>,
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
	Jonas Karlman <jonas@...boo.se>,
	Jernej Skrabec <jernej.skrabec@...il.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	Luca Ceresoli <luca.ceresoli@...tlin.com>,
	dri-devel@...ts.freedesktop.org, imx@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] drm/bridge: imx8qxp-ldb: Fix NULL pointer
 dereference in imx8qxp_ldb_bridge_destroy()

On Fri, Jan 23, 2026 at 05:22:15PM +0800, Liu Ying wrote:
> Pointer bridge->driver_private in imx8qxp_ldb_bridge_destroy() is NULL
> when a LDB channel is unavailable or imx8qxp_ldb_probe() returns error,
> because ldb_add_bridge_helper() is the last function called from
> imx8qxp_ldb_probe() and it doesn't initialize bridge->driver_private if
> a LDB channel is unavailable.  The NULL pointer would be set to pointer
> ldb_ch and then NULL pointer ldb_ch would be dereferenced.  Fix this
> by returning early from imx8qxp_ldb_bridge_destroy() if !ldb_ch is true.
>
> Fixes: 32529d384cea ("drm/bridge: imx8qxp-ldb: convert to of_drm_find_and_get_bridge()")
> Signed-off-by: Liu Ying <victor.liu@....com>

Reviewed-by: Frank Li <Frank.Li@....com>
> ---
>  drivers/gpu/drm/bridge/imx/imx8qxp-ldb.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/imx/imx8qxp-ldb.c b/drivers/gpu/drm/bridge/imx/imx8qxp-ldb.c
> index 43b328cb5314..ada11eed13cf 100644
> --- a/drivers/gpu/drm/bridge/imx/imx8qxp-ldb.c
> +++ b/drivers/gpu/drm/bridge/imx/imx8qxp-ldb.c
> @@ -65,9 +65,12 @@ static inline struct imx8qxp_ldb *base_to_imx8qxp_ldb(struct ldb *base)
>  static void imx8qxp_ldb_bridge_destroy(struct drm_bridge *bridge)
>  {
>  	struct ldb_channel *ldb_ch = bridge->driver_private;
> -	struct ldb *ldb = ldb_ch->ldb;
> -	struct imx8qxp_ldb *imx8qxp_ldb = base_to_imx8qxp_ldb(ldb);
> +	struct imx8qxp_ldb *imx8qxp_ldb;
> +
> +	if (!ldb_ch)
> +		return;
>
> +	imx8qxp_ldb = base_to_imx8qxp_ldb(ldb_ch->ldb);
>  	drm_bridge_put(imx8qxp_ldb->companion);
>  }
>
>
> --
> 2.43.0
>