drm/msm: Init mm_list before accessing it for use_vram path

Fix NULL pointer dereference caused by update_inactive()
trying to list_del() an uninitialized mm_list who's
prev/next pointers are NULL.

Fixes: 64fcbde772c7 ("drm/msm: Track potentially evictable objects")
Signed-off-by: Alexey Minnekhanov <alexeymin@postmarketos.org>
Link: https://lore.kernel.org/r/20210518102624.1193955-1-alexeymin@postmarketos.org
Signed-off-by: Rob Clark <robdclark@chromium.org>

diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
index 56df86e..369d91e 100644 (file)
--- a/drivers/gpu/drm/msm/msm_gem.c
+++ b/drivers/gpu/drm/msm/msm_gem.c
@@ -1241,6 +1241,13 @@ static struct drm_gem_object *_msm_gem_new(struct drm_device *dev,
 
                to_msm_bo(obj)->vram_node = &vma->node;
 
+               /* Call chain get_pages() -> update_inactive() tries to
+                * access msm_obj->mm_list, but it is not initialized yet.
+                * To avoid NULL pointer dereference error, initialize
+                * mm_list to be empty.
+                */
+               INIT_LIST_HEAD(&msm_obj->mm_list);
+
                msm_gem_lock(obj);
                pages = get_pages(obj);
                msm_gem_unlock(obj);