No root password is set. How can I change sudoers file permissions?

If you do not have the root password, How can I change the sudoers file permission?-General Linux technology-Linux technology and application information. For more information, see the following. Cyt @ ubuntu:/etc $ ls-l | grep sudoer
-Rwxrwxrwx 1 root 652 sudoers
Drwxr-xr-x 2 root 4096 2010-04-29 05:18 sudoers. d
Cyt @ ubuntu:/etc $ sudo chmod 0440 sudoers
Sudo:/etc/sudoers is mode 0777, shocould be 0440
Sudo: no valid sudoers sources found, quitting
Cyt @ ubuntu:/etc $ chmod 0440 sudoers
Chmod: changing permissions of 'sudoers': Operation not permitted
Cyt @ ubuntu:/etc $ su-
Password:
Su: Authentication failure
Cyt @ ubuntu:/etc $