[PATCH] drm: Remove "protection" around drm_vma_offset_manager_destroy()

From: Chris Wilson <chris@chris-wilson.co.uk>
To: dri-devel@lists.freedesktop.org
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>,
	intel-gfx@lists.freedesktop.org,
	Davidlohr Bueso <dave@stgolabs.net>,
	Liviu Dudau <Liviu.Dudau@arm.com>
Subject: [PATCH] drm: Remove "protection" around drm_vma_offset_manager_destroy()
Date: Mon,  3 Sep 2018 10:31:55 +0100	[thread overview]
Message-ID: <20180903093155.3825-1-chris@chris-wilson.co.uk> (raw)

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>
---
 drivers/gpu/drm/drm_vma_manager.c | 3 ---
 1 file changed, 3 deletions(-)

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);
 
-- 
2.19.0.rc1

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