drm/msm: Fix possible uninitialized access in fbdev

Do not run drm_fb_helper_unprepare() if fbdev allocation fails. Avoids
access to an uninitialized pointer. Original bug report is at [1].

Reported-by: kernel test robot <[email protected]>
Signed-off-by: Thomas Zimmermann <[email protected]>
Fixes: 3fb1f62 ("drm/fb-helper: Remove drm_fb_helper_unprepare() from drm_fb_helper_fini()")
Link: https://lore.kernel.org/oe-kbuild-all/[email protected]/ # 1
Reviewed-by: Dmitry Baryshkov <[email protected]>
Patchwork: https://patchwork.freedesktop.org/patch/523715/
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Rob Clark <[email protected]>

Author: Thomas Zimmermann

drivers/gpu/drm/msm/msm_fbdev.c

@@ -136,13 +136,13 @@ static const struct drm_fb_helper_funcs msm_fb_helper_funcs = {
 struct drm_fb_helper *msm_fbdev_init(struct drm_device *dev)
 {
 	struct msm_drm_private *priv = dev->dev_private;
-	struct msm_fbdev *fbdev = NULL;
+	struct msm_fbdev *fbdev;
 	struct drm_fb_helper *helper;
 	int ret;
 
 	fbdev = kzalloc(sizeof(*fbdev), GFP_KERNEL);
 	if (!fbdev)
-		goto fail;
+		return NULL;
 
 	helper = &fbdev->base;