linux-kernel - [PATCH] drm: bridge: cdns-mhdp8546: Fix possible null pointer dereference

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Date: Mon, 8 Apr 2024 15:58:10 +0300
From: Aleksandr Mishin <amishin@...rgos.ru>
To: Swapnil Jakhade <sjakhade@...ence.com>
CC: Aleksandr Mishin <amishin@...rgos.ru>, 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>,
	Daniel Vetter <daniel@...ll.ch>, Tomi Valkeinen <tomi.valkeinen@...com>,
	Uwe Kleine-König <u.kleine-koenig@...gutronix.de>, Nikhil
 Devshatwar <nikhil.nd@...com>, Aradhya Bhatia <a-bhatia1@...com>, Jani Nikula
	<jani.nikula@...el.com>, Rob Herring <robh@...nel.org>, Zhu Wang
	<wangzhu9@...wei.com>, Yuti Amonkar <yamonkar@...ence.com>, Jyri Sarha
	<jsarha@...com>, Quentin Schulz <quentin.schulz@...e-electrons.com>,
	<dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
	<lvc-project@...uxtesting.org>
Subject: [PATCH] drm: bridge: cdns-mhdp8546: Fix possible null pointer dereference

In cdns_mhdp_atomic_enable(), the return value of drm_mode_duplicate() is
assigned to mhdp_state->current_mode, and there is a dereference of it in
drm_mode_set_name(), which will lead to a NULL pointer dereference on
failure of drm_mode_duplicate().

Fix this bug add a check of mhdp_state->current_mode.

Fixes: fb43aa0acdfd ("drm: bridge: Add support for Cadence MHDP8546 DPI/DP bridge")
Signed-off-by: Aleksandr Mishin <amishin@...rgos.ru>
---
 drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
index e226acc5c15e..8a91ef0ae065 100644
--- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
+++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
@@ -2059,6 +2059,9 @@ static void cdns_mhdp_atomic_enable(struct drm_bridge *bridge,
 	mhdp_state = to_cdns_mhdp_bridge_state(new_state);
 
 	mhdp_state->current_mode = drm_mode_duplicate(bridge->dev, mode);
+	if (!mhdp_state->current_mode)
+		return;
+
 	drm_mode_set_name(mhdp_state->current_mode);
 
 	dev_dbg(mhdp->dev, "%s: Enabling mode %s\n", __func__, mode->name);
-- 
2.30.2