linux-kernel - [PATCH][next] drm/msm: Fix dereference of pointer minor before null check

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Message-ID: <20250730142905.2080035-1-colin.i.king@gmail.com>
Date: Wed, 30 Jul 2025 15:29:05 +0100
From: Colin Ian King <colin.i.king@...il.com>
To: Rob Clark <robin.clark@....qualcomm.com>,
	Dmitry Baryshkov <lumag@...nel.org>,
	Abhinav Kumar <abhinav.kumar@...ux.dev>,
	Jessica Zhang <jessica.zhang@....qualcomm.com>,
	Sean Paul <sean@...rly.run>,
	Marijn Suijten <marijn.suijten@...ainline.org>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>,
	linux-arm-msm@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	freedreno@...ts.freedesktop.org
Cc: kernel-janitors@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH][next] drm/msm: Fix dereference of pointer minor before null check

Currently the pointer minor is being dereferenced before it is null
checked, leading to a potential null pointer dereference issue. Fix this
by dereferencing the pointer only after it has been null checked. Also
Replace minor->dev with dev.

Fixes: 4f89cf40d01e ("drm/msm: bail out late_init_minor() if it is not a GPU device")
Signed-off-by: Colin Ian King <colin.i.king@...il.com>
---
 drivers/gpu/drm/msm/msm_debugfs.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/msm/msm_debugfs.c b/drivers/gpu/drm/msm/msm_debugfs.c
index bbda865addae..97dc70876442 100644
--- a/drivers/gpu/drm/msm/msm_debugfs.c
+++ b/drivers/gpu/drm/msm/msm_debugfs.c
@@ -325,25 +325,28 @@ static struct drm_info_list msm_debugfs_list[] = {
 
 static int late_init_minor(struct drm_minor *minor)
 {
-	struct drm_device *dev = minor->dev;
-	struct msm_drm_private *priv = dev->dev_private;
+	struct drm_device *dev;
+	struct msm_drm_private *priv;
 	int ret;
 
 	if (!minor)
 		return 0;
 
+	dev = minor->dev;
+	priv = dev->dev_private;
+
 	if (!priv->gpu_pdev)
 		return 0;
 
 	ret = msm_rd_debugfs_init(minor);
 	if (ret) {
-		DRM_DEV_ERROR(minor->dev->dev, "could not install rd debugfs\n");
+		DRM_DEV_ERROR(dev->dev, "could not install rd debugfs\n");
 		return ret;
 	}
 
 	ret = msm_perf_debugfs_init(minor);
 	if (ret) {
-		DRM_DEV_ERROR(minor->dev->dev, "could not install perf debugfs\n");
+		DRM_DEV_ERROR(dev->dev, "could not install perf debugfs\n");
 		return ret;
 	}
 
-- 
2.50.0