Simply complain if the combined result of start_page and num_pages goes over

the pages bo has. Let me know if the added warning is too heavy a hammer.

Cc: Christian Koenig <christian.koenig@amd.com>

Cc: Huang Rui <ray.huang@amd.com>

Cc: Junwei Zhang <Jerry.Zhang@amd.com>

Signed-off-by: Hillf Danton <hdanton@sina.com>

---

--- a/drivers/gpu/drm/ttm/ttm_bo_util.c 2019-04-02 09:27:24.521761100 +0800

+++ b/drivers/gpu/drm/ttm/ttm_bo_util.c     2019-04-02 09:37:52.108898500 +0800

@@ -631,6 +631,8 @@ int ttm_bo_kmap(struct ttm_buffer_object

             return -EINVAL;

      if (start_page > bo->num_pages)

             return -EINVAL;

+    if (WARN_ON(start_page > bo->num_pages - num_pages))

+           return -EINVAL;

       (void) ttm_mem_io_lock(man, false);

      ret = ttm_mem_io_reserve(bo->bdev, &bo->mem);

--