linux-kernel - [PATCH] drm/vc4: hdmi: Fix pointer dereference before check

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Message-Id: <20221029093413.546103-1-jose.exposito89@gmail.com>
Date:   Sat, 29 Oct 2022 11:34:13 +0200
From:   José Expósito <jose.exposito89@...il.com>
To:     mripard@...nel.org
Cc:     emma@...olt.net, airlied@...il.com, daniel@...ll.ch,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        José Expósito <jose.exposito89@...il.com>
Subject: [PATCH] drm/vc4: hdmi: Fix pointer dereference before check

Commit 6bed2ea3cb38 ("drm/vc4: hdmi: Reset link on hotplug") introduced
the vc4_hdmi_reset_link() function. This function dereferences the
"connector" pointer before checking whether it is NULL or not.

Rework variable assignment to avoid this issue.

Fixes: 6bed2ea3cb38 ("drm/vc4: hdmi: Reset link on hotplug")
Signed-off-by: José Expósito <jose.exposito89@...il.com>
---
 drivers/gpu/drm/vc4/vc4_hdmi.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index 4a73fafca51b..07d058b6afb7 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -319,9 +319,9 @@ static int reset_pipe(struct drm_crtc *crtc,
 static int vc4_hdmi_reset_link(struct drm_connector *connector,
 			       struct drm_modeset_acquire_ctx *ctx)
 {
-	struct drm_device *drm = connector->dev;
-	struct vc4_hdmi *vc4_hdmi = connector_to_vc4_hdmi(connector);
-	struct drm_encoder *encoder = &vc4_hdmi->encoder.base;
+	struct drm_device *drm;
+	struct vc4_hdmi *vc4_hdmi;
+	struct drm_encoder *encoder;
 	struct drm_connector_state *conn_state;
 	struct drm_crtc_state *crtc_state;
 	struct drm_crtc *crtc;
@@ -332,6 +332,10 @@ static int vc4_hdmi_reset_link(struct drm_connector *connector,
 	if (!connector)
 		return 0;
 
+	drm = connector->dev;
+	vc4_hdmi = connector_to_vc4_hdmi(connector);
+	encoder = &vc4_hdmi->encoder.base;
+
 	ret = drm_modeset_lock(&drm->mode_config.connection_mutex, ctx);
 	if (ret)
 		return ret;
-- 
2.25.1