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

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Message-Id: <20230324035909.1727356-1-treapking@chromium.org>
Date:   Fri, 24 Mar 2023 11:59:09 +0800
From:   Pin-yen Lin <treapking@...omium.org>
To:     Douglas Anderson <dianders@...omium.org>,
        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>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Pin-yen Lin <treapking@...omium.org>
Subject: [PATCH] drm/bridge: ps8640: Return NULL immediately when EDID read fail

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