criu: warn about cgroup hierarchies without controllers

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/src/lxc/criu.c b/src/lxc/criu.c
index c5d70aa229c9b73202e79a9df63f9b183a25e79e..e934f9e278b933d972bfef7b206cd242249e9665 100644 (file)
--- a/src/lxc/criu.c
+++ b/src/lxc/criu.c
@@ -324,11 +324,16 @@ static int exec_criu(struct cgroup_ops *cgroup_ops, struct lxc_conf *conf,
                        return log_error_errno(-ENOMEM, ENOMEM, "Failed to remove extraneous slashes from \"%s\"", tmp);
                free_move_ptr(cgroup_base_path, tmp);
 
-               controllers = lxc_string_join(",", (const char **)controllers_list, false);
-               if (!controllers)
-                       return log_error_errno(-ENOMEM, ENOMEM, "Failed to join controllers");
+               if (controllers_list[0]) {
+                       controllers = lxc_string_join(",", (const char **)controllers_list, false);
+                       if (!controllers)
+                               return log_error_errno(-ENOMEM, ENOMEM, "Failed to join controllers");
 
-               ret = sprintf(buf, "%s:%s", controllers, cgroup_base_path);
+                       ret = sprintf(buf, "%s:%s", controllers, cgroup_base_path);
+               } else {
+                       WARN("No cgroup controllers configured in container's cgroup %s", cgroup_base_path);
+                       ret = sprintf(buf, "%s", cgroup_base_path);
+               }
                if (ret < 0 || ret >= sizeof(buf))
                        return log_error_errno(-EIO, EIO, "sprintf of cgroup root arg failed");