4.14-stable patches

[thirdparty/kernel/stable-queue.git] / releases / 3.10.56 / drm-ttm-fix-possible-division-by-0-in-ttm_dma_pool_shrink_scan.patch

From 11e504cc705e8ccb06ac93a276e11b5e8fee4d40 Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Date: Sun, 3 Aug 2014 19:59:35 +0900
Subject: drm/ttm: Fix possible division by 0 in ttm_dma_pool_shrink_scan().

From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>

commit 11e504cc705e8ccb06ac93a276e11b5e8fee4d40 upstream.

list_empty(&_manager->pools) being false before taking _manager->lock
does not guarantee that _manager->npools != 0 after taking _manager->lock
because _manager->npools is updated under _manager->lock.

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/gpu/drm/ttm/ttm_page_alloc_dma.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
+++ b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
@@ -1016,6 +1016,8 @@ static int ttm_dma_pool_mm_shrink(struct
 		return 0;
 
 	mutex_lock(&_manager->lock);
+	if (!_manager->npools)
+		goto out;
 	pool_offset = pool_offset % _manager->npools;
 	list_for_each_entry(p, &_manager->pools, pools) {
 		unsigned nr_free;
@@ -1033,6 +1035,7 @@ static int ttm_dma_pool_mm_shrink(struct
 			 p->pool->dev_name, p->pool->name, current->pid,
 			 nr_free, shrink_pages);
 	}
+out:
 	mutex_unlock(&_manager->lock);
 	/* return estimated number of unused pages in pool */
 	return ttm_dma_pool_get_num_unused_pages();