USN-3540-2: Linux kernel (Xenial HWE) vulnerabilities

Ubuntu Security Notice USN-3540-2

22nd January, 2018

linux-lts-xenial, linux-aws vulnerabilities

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

  • Ubuntu 14.04 LTS

Summary

Several security issues were addressed in the Linux kernel.

Software description

  • linux-aws - Linux kernel for Amazon Web Services (AWS) systems
  • linux-lts-xenial - Linux hardware enablement kernel from Xenial for Trusty

Details

USN-3540-1 addressed vulnerabilities in the Linux kernel for Ubuntu
16.04 LTS. This update provides the corresponding updates for the
Linux Hardware Enablement (HWE) kernel from Ubuntu 16.04 LTS for
Ubuntu 14.04 LTS.

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. This update provides mitigations for the
i386 (CVE-2017-5753 only), amd64, ppc64el, and s390x architectures.
(CVE-2017-5715, CVE-2017-5753)

USN-3522-2 mitigated CVE-2017-5754 (Meltdown) for the amd64
architecture in the Linux Hardware Enablement (HWE) kernel from Ubuntu
16.04 LTS for Ubuntu 14.04 LTS. This update provides the corresponding
mitigations for the ppc64el architecture. Original advisory details:

Jann Horn discovered that microprocessors utilizing speculative
execution and indirect branch prediction may allow unauthorized memory
reads via sidechannel attacks. This flaw is known as Meltdown. A local
attacker could use this to expose sensitive information, including
kernel memory. (CVE-2017-5754)

Update instructions

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

Ubuntu 14.04 LTS:
linux-image-4.4.0-111-powerpc-smp 4.4.0-111.134~14.04.1
linux-image-powerpc-smp-lts-xenial 4.4.0.111.95
linux-image-4.4.0-111-powerpc64-smp 4.4.0-111.134~14.04.1
linux-image-4.4.0-111-powerpc64-emb 4.4.0-111.134~14.04.1
linux-image-4.4.0-1011-aws 4.4.0-1011.11
linux-image-4.4.0-111-powerpc-e500mc 4.4.0-111.134~14.04.1
linux-image-lowlatency-lts-xenial 4.4.0.111.95
linux-image-generic-lts-xenial 4.4.0.111.95
linux-image-4.4.0-111-lowlatency 4.4.0-111.134~14.04.1
linux-image-aws 4.4.0.1011.11
linux-image-powerpc64-smp-lts-xenial 4.4.0.111.95
linux-image-powerpc64-emb-lts-xenial 4.4.0.111.95
linux-image-4.4.0-111-generic 4.4.0-111.134~14.04.1
linux-image-powerpc-e500mc-lts-xenial 4.4.0.111.95

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

CVE-2017-5715, CVE-2017-5753, CVE-2017-5754, https://wiki.ubuntu.com/SecurityTeam/KnowledgeBase/SpectreAndMeltdown