USN-3549-1: Linux kernel (KVM) vulnerabilities

Ubuntu Security Notice USN-3549-1

29th January, 2018

linux-kvm vulnerabilities

A security issue affects these releases of Ubuntu and its
derivatives:

Ubuntu 16.04 LTS

Summary

Several security issues were fixed in the Linux kernel.

Software description

linux-kvm
– Linux kernel for cloud environments

Details

Jann Horn discovered that microprocessors utilizing speculative
execution and branch prediction may allow unauthorized memory
reads via sidechannel attacks. This flaw is known as Spectre. A
local attacker could use this to expose sensitive information,
including kernel memory. (CVE-2017-5715, CVE-2017-5753)

Update instructions

The problem can be corrected by updating your system to the following
package version:

Ubuntu 16.04 LTS:: linux-image-4.4.0-1017-kvm

4.4.0-1017.22; linux-image-kvm

4.4.0.1017.16

To update your system, please follow these instructions:
https://wiki.ubuntu.com/Security/Upgrades.

Please note that fully mitigating CVE-2017-5715 (Spectre Variant 2)
requires corresponding processor microcode/firmware updates or,
in virtual environments, hypervisor updates. On i386 and amd64
architectures, the IBRS and IBPB features are required to enable the
kernel mitigations. Ubuntu is working with Intel and AMD to provide
future microcode updates that implement IBRS and IBPB as they are made
available. Ubuntu users with a processor from a different vendor should
contact the vendor to identify necessary firmware updates. Ubuntu
will provide corresponding QEMU updates in the future for users of
self-hosted virtual environments in coordination with upstream QEMU.
Ubuntu users in cloud environments should contact the cloud provider
to confirm that the hypervisor has been updated to expose the new
CPU features to virtual machines.

After a standard system update you need to reboot your computer to
apply the necessary changes.