drm/gem: drm_gem_dumb_map_offset(): reject dma-buf

Reject mapping an imported dma-buf since is's an invalid use-case.

Cc: Philipp Zabel <[email protected]>
Cc: Laurent Pinchart <[email protected]>
Cc: Sean Paul <[email protected]>
Cc: Daniel Vetter <[email protected]>
Signed-off-by: Noralf Trønnes <[email protected]>
Acked-by: Daniel Vetter <[email protected]>
Acked-by: Eric Anholt <[email protected]>
Acked-by: Thierry Reding <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

drivers/gpu/drm/drm_gem.c

@@ -333,6 +333,12 @@ int drm_gem_dumb_map_offset(struct drm_file *file, struct drm_device *dev,
 	if (!obj)
 		return -ENOENT;
 
+	/* Don't allow imported objects to be mapped */
+	if (obj->import_attach) {
+		ret = -EINVAL;
+		goto out;
+	}
+
 	ret = drm_gem_create_mmap_offset(obj);
 	if (ret)
 		goto out;