From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Mon, 3 Sep 2018 09:31:55 +0000 (+0100)
Subject: drm: Remove "protection" around drm_vma_offset_manager_destroy()
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=5ddd6582cd7ba018b7527eed1777b7d83e6d9b62;p=openwrt%2Fstaging%2Fblogic.git

drm: Remove "protection" around drm_vma_offset_manager_destroy()

Using a spinlock to serialize the destroy function, within the destroy
function itself does not prevent the buggy driver from shooting
themselves in the foot - either way they still have a use-after-free
issue.

Reported-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Liviu Dudau <Liviu.Dudau@arm.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20180903093155.3825-1-chris@chris-wilson.co.uk
---

diff --git a/drivers/gpu/drm/drm_vma_manager.c b/drivers/gpu/drm/drm_vma_manager.c
index a6b2fe36b025..c5d0d2358301 100644
--- a/drivers/gpu/drm/drm_vma_manager.c
+++ b/drivers/gpu/drm/drm_vma_manager.c
@@ -103,10 +103,7 @@ EXPORT_SYMBOL(drm_vma_offset_manager_init);
  */
 void drm_vma_offset_manager_destroy(struct drm_vma_offset_manager *mgr)
 {
-	/* take the lock to protect against buggy drivers */
-	write_lock(&mgr->vm_lock);
 	drm_mm_takedown(&mgr->vm_addr_space_mm);
-	write_unlock(&mgr->vm_lock);
 }
 EXPORT_SYMBOL(drm_vma_offset_manager_destroy);