Speculative Execution Attacks

Last changed: 2018-01-10

Important

UPDATE 2018-01-10 Kernel patches for Ubuntu 16.04 LTS and 17.10 are now available. See instructions below. New instances will have the updated kernel.

UPDATE 2018-01-09 Contrary to what’s been said in this security advisory earlier, a kernel patch for Ubuntu is not yet available, however, it is expected by January 9, 2018. We’re sorry to have provided misleading information and will notitfy our users when a patch is available.

Background Information

In January 2018, multiple microarchitectural (hardware) implementation issues surfaced, affecting many modern microprocessors. These issues require updates to the operating system (e.g. Linux/Windows kernel) and/or in combination with a microcode update. An unprivileged attacker can use these flaws to bypass conventional memory security restrictions in order to gain read access to privileged memory that would otherwise be inaccessible. There are 3 known CVEs related to this issue in combination with Intel, AMD, and ARM architectures.

With an infrastructure-as-a-service cloud like UH-IaaS, the customer is responsible for the security of the instances running in his/her project. As the service provider, we will make available updated images in which these speculative execution issues are mitigated. However, the customer still needs to take action either by reprovisioning the instances using the updated images, or by updating any running instances using the appropriate tools for the operating system.

For more information regarding these security issues, refer to Additional References.

Updating your Instances

This paragraph describes in detail how to update any of the standard Linux distributions offered in UH-IaaS.

CentOS

In order to update an instance running CentOS, perform the following:

  1. Log in as user “centos”:

    $ ssh centos@<instance-ip-address>
    
  2. Run “yum upgrade” using sudo:

    $ sudo yum upgrade
    
  3. Reboot the instance:

    $ sudo reboot
    
  4. Check that the running kernel has been updated:

    $ ssh centos@<instance-ip-address> 'uname -sr'
    Linux 3.10.0-693.11.6.el7.x86_64
    

    The output above shows the latest kernel for CentOS 7 as of January 8, 2018.

Fedora

In order to update an instance running Fedora, perform the following:

  1. Log in as user “fedora”:

    $ ssh fedora@<instance-ip-address>
    
  2. Run “dnf upgrade” using sudo:

    $ sudo dnf upgrade --refresh
    
  3. Reboot the instance:

    $ sudo reboot
    
  4. Check that the running kernel has been updated:

    $ ssh fedora@<instance-ip-address> 'uname -sr'
    Linux 4.14.11-300.fc27.x86_64
    

    The output above shows the latest kernel for Fedora 27 as of January 8, 2018.

Debian

In order to update an instance running Debian, perform the following:

  1. Log in as user “debian”:

    $ ssh debian@<instance-ip-address>
    
  2. Update and upgrade using sudo:

    $ sudo apt-get update && sudo apt-get -y dist-upgrade
    
  3. Reboot the instance:

    $ sudo reboot
    
  4. Check that the running kernel has been updated:

    $ ssh debian@<instance-ip-address> 'uname -srv'
    Linux 4.9.0-5-amd64 #1 SMP Debian 4.9.65-3+deb9u2 (2018-01-04)
    

    The output above shows the latest kernel for Debian 9 as of January 8, 2018.

Ubuntu

Ubuntu Cloud images are preinstalled with Unattended Upgrades meaning security updates will be automacially installed when they’re available. However, you need to reboot your instances in order to actually run the updated kernel.

  1. Check your kernel version

    $ ssh ubuntu@<instance-ip-address> 'uname -srv'
    

    You should get the following output if you have the updated kernel in 16.04 LTS:

    Linux 4.4.0-108-generic #131-Ubuntu SMP Sun Jan 7 14:34:49 UTC 2018
    

    or in Ubuntu 17.10:

    Linux 4.13.0-25-generic #29-Ubuntu SMP Mon Jan 8 21:14:41 UTC 2018
    
  2. If the output shows something else, check the unattended upgrades log:

    $ ssh ubuntu@<instance-ip-address>
    $ less /var/log/unattended-upgrades/unattended-upgrades.log
    

    and look for a line similar to this:

    2018-01-10 09:25:25,440 INFO Packages that will be upgraded: linux-headers-generic linux-headers-virtual linux-image-virtual linux-virtual
    
  3. If you have something that looks like the above, reboot your instance and check your kernel version again

    $ sudo reboot
    
  4. If you don’t, or if you’ve disabled or uninstalled Unattended Upgrades for some reason, proceed with manual updating shown bellow.

In order to manually update an instance running Ubuntu, perform the following:

  1. Log in as user “ubuntu”:

    $ ssh ubuntu@<instance-ip-address>
    
  2. Update and upgrade using sudo:

    $ sudo apt-get update && sudo apt-get -y dist-upgrade
    
  3. Reboot the instance:

    $ sudo reboot
    
  4. Check that the running kernel has been updated:

    $ ssh ubuntu@<instance-ip-address> 'uname -srv'
    Linux 4.4.0-108-generic #131-Ubuntu SMP Sun Jan 7 14:34:49 UTC 2018
    

    if you’re running 16.04 LTS or

    $ ssh ubuntu@<instance-ip-address> 'uname -srv'
    Linux 4.13.0-25-generic #29-Ubuntu SMP Mon Jan 8 21:14:41 UTC 2018
    

    if you’re running 17.10.

    The output above shows the latest kernel for Ubuntu 16.04 LTS and 17.10 as of January 10, 2018.