[PATCH 1/5] gpu/drm/ttm: Fix possible division by 0 in ttm_dma_pool_shrink_scan().

[Tetsuo Handa]

>From 5c2f18ca300a1182e40f143b81e927426232b005 Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp>
Date: Sun, 3 Aug 2014 19:59:35 +0900
Subject: [PATCH 1/5] gpu/drm/ttm: Fix possible division by 0 in 
ttm_dma_pool_shrink_scan().

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 at I-love.SAKURA.ne.jp>
Cc: stable <stable at kernel.org> [3.3+]
---
 drivers/gpu/drm/ttm/ttm_page_alloc_dma.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c 
b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
index fb8259f..b751fff 100644
--- a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
+++ b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
@@ -1015,6 +1015,8 @@ ttm_dma_pool_shrink_scan(struct shrinker *shrink, struct 
shrink_control *sc)
                return SHRINK_STOP;

        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;
@@ -1034,6 +1036,7 @@ ttm_dma_pool_shrink_scan(struct shrinker *shrink, struct 
shrink_control *sc)
                         p->pool->dev_name, p->pool->name, current->pid,
                         nr_free, shrink_pages);
        }
+out:
        mutex_unlock(&_manager->lock);
        return freed;
 }
-- 
1.7.1