diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index aa312b0dc3ec..b99c862a2e3f 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -812,7 +812,9 @@ static bool new_idmap_permitted(const struct file *file,
 				struct user_namespace *ns, int cap_setid,
 				struct uid_gid_map *new_map)
 {
-	/* Allow mapping to your own filesystem ids */
+	/* Don't allow mappings that would allow anything that wouldn't
+	 * be allowed without the establishment of unprivileged mappings.
+	 */
 	if ((new_map->nr_extents == 1) && (new_map->extent[0].count == 1)) {
 		u32 id = new_map->extent[0].lower_first;
 		if (cap_setid == CAP_SETUID) {