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

From: Alexey Minnekhanov <alexeymin@postmarketos.org>
To: Rob Clark <robdclark@gmail.com>, Sean Paul <sean@poorly.run>,
	David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
	linux-arm-msm@vger.kernel.org (open list:DRM DRIVER FOR MSM
	ADRENO GPU),
	dri-devel@lists.freedesktop.org (open list:DRM DRIVER FOR MSM
	ADRENO GPU),
	freedreno@lists.freedesktop.org (open list:DRM DRIVER FOR MSM
	ADRENO GPU), linux-kernel@vger.kernel.org (open list)
Cc: ~postmarketos/upstreaming@lists.sr.ht,
	Alexey Minnekhanov <alexeymin@postmarketos.org>
Subject: [PATCH] drm/msm: Init mm_list before accessing it for use_vram path
Date: Tue, 18 May 2021 13:26:24 +0300	[thread overview]
Message-ID: <20210518102624.1193955-1-alexeymin@postmarketos.org> (raw)

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

