drm/msm: return an error pointer in msm_gem_prime_get_sg_table()

[ Upstream commit cf575e3 ]

The msm_gem_prime_get_sg_table() needs to return error pointers on
error.  This is called from drm_gem_map_dma_buf() and returning a
NULL will lead to a crash in that function.

Fixes: ac45146 ("drm/msm: fix msm_gem_prime_get_sg_table()")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/485023/
Link: https://lore.kernel.org/r/YnOmtS5tfENywR9m@kili
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/gpu/drm/msm/msm_gem_prime.c

@@ -17,7 +17,7 @@ struct sg_table *msm_gem_prime_get_sg_table(struct drm_gem_object *obj)
 	int npages = obj->size >> PAGE_SHIFT;
 
 	if (WARN_ON(!msm_obj->pages))  /* should have already pinned! */
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	return drm_prime_pages_to_sg(obj->dev, msm_obj->pages, npages);
 }