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    Subject[PATCH 3.16 012/357] drm/ttm: Fix possible division by 0 in ttm_dma_pool_shrink_scan().
    Date
    3.16-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    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
    @@ -1015,6 +1015,8 @@ ttm_dma_pool_shrink_scan(struct shrinker
    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
    p->pool->dev_name, p->pool->name, current->pid,
    nr_free, shrink_pages);
    }
    +out:
    mutex_unlock(&_manager->lock);
    return freed;
    }



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