drm/ttm: Fix possible division by 0 in ttm_dma_pool_shrink_scan().

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>

diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
index b8b394319b45947facd37036817b73ac39a2661c..e9f65ad2a0eba3c7f5eba59d3344c26ddd366dd6 100644 (file)
--- 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 shrinker *shrink,
                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 shrinker *shrink,
                         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();