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

* [PATCH] drm/msm: Init mm_list before accessing it for use_vram path
@ 2021-05-18 10:26 Alexey Minnekhanov
  0 siblings, 0 replies; only message in thread
From: Alexey Minnekhanov @ 2021-05-18 10:26 UTC (permalink / raw)
  To: Rob Clark, Sean Paul, David Airlie, Daniel Vetter,
	open list:DRM DRIVER FOR MSM ADRENO GPU,
	open list:DRM DRIVER FOR MSM ADRENO GPU,
	open list:DRM DRIVER FOR MSM ADRENO GPU, open list
  Cc: ~postmarketos/upstreaming, Alexey Minnekhanov

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

Signed-off-by: Alexey Minnekhanov <alexeymin@postmarketos.org>
---
 drivers/gpu/drm/msm/msm_gem.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
index b199942266a26..b8c873fc63a78 100644
--- a/drivers/gpu/drm/msm/msm_gem.c
+++ b/drivers/gpu/drm/msm/msm_gem.c
@@ -1227,6 +1227,13 @@ 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);
-- 
2.26.3


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