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

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Message-Id: <20260123-imx8qxp-drm-bridge-fixes-v1-1-8bb85ada5866@nxp.com>
Date: Fri, 23 Jan 2026 17:22:15 +0800
From: Liu Ying <victor.liu@....com>
To: 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>
Cc: dri-devel@...ts.freedesktop.org, imx@...ts.linux.dev, 
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 Liu Ying <victor.liu@....com>
Subject: [PATCH 1/3] drm/bridge: imx8qxp-ldb: Fix NULL pointer dereference
 in imx8qxp_ldb_bridge_destroy()

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>
---
 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