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

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

[Colin Ian King]

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@gmail.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

Re: [PATCH] drm/msm: Fix dereference of pointer minor before null check

[Markus Elfring]

…
> by dereferencing the pointer only after it has been null checked. Also
> Replace minor->dev with dev.

I suggest to separate desirable changes into another patch series.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?h=v6.16#n81

Regards,
Markus