FYI, Ubuntu released updates today for Meltdown:

Ubuntu 16.04 LTS: https://usn.ubuntu.com/usn/usn-3522-1/

Ubuntu 14.04 LTS: https://usn.ubuntu.com/usn/usn-3522-2/

Ubuntu 17.10: https://usn.ubuntu.com/usn/usn-3523-1/