linux-kernel - [PATCH v2 2/2] drm/vc4: hdmi: Fix pointer dereference before check

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Date:   Thu, 10 Nov 2022 14:47:52 +0100
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 v2 2/2] 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 | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index a49f88e5d2b9..6b223a5fcf6f 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -318,8 +318,8 @@ 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_device *drm;
+	struct vc4_hdmi *vc4_hdmi;
 	struct drm_connector_state *conn_state;
 	struct drm_crtc_state *crtc_state;
 	struct drm_crtc *crtc;
@@ -330,6 +330,7 @@ static int vc4_hdmi_reset_link(struct drm_connector *connector,
 	if (!connector)
 		return 0;
 
+	drm = connector->dev;
 	ret = drm_modeset_lock(&drm->mode_config.connection_mutex, ctx);
 	if (ret)
 		return ret;
@@ -347,6 +348,7 @@ static int vc4_hdmi_reset_link(struct drm_connector *connector,
 	if (!crtc_state->active)
 		return 0;
 
+	vc4_hdmi = connector_to_vc4_hdmi(connector);
 	if (!vc4_hdmi_supports_scrambling(vc4_hdmi))
 		return 0;
 
-- 
2.25.1