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

29 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 versions:

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.

References