[USN-3522-4] Linux kernel (Xenial HWE) regression

[Steve Beattie]

==========================================================================
Ubuntu Security Notice USN-3522-4
January 10, 2018

linux-lts-xenial regression
==========================================================================

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

- Ubuntu 14.04 LTS

Summary:

USN-3522-2 introduced a regression in the Linux Hardware Enablement kernel.

Software Description:
- linux-lts-xenial: Linux hardware enablement kernel from Xenial for Trusty

Details:

USN-3522-2 fixed a vulnerability in the Linux Hardware Enablement
kernel for Ubuntu 14.04 LTS to address Meltdown (CVE-2017-5754).
Unfortunately, that update introduced a regression where a few systems
failed to boot successfully. This update fixes the problem.

We apologize for the inconvenience.

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.

Update instructions:

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

Ubuntu 14.04 LTS:
  linux-image-4.4.0-109-generic   4.4.0-109.132~14.04.1
  linux-image-4.4.0-109-lowlatency  4.4.0-109.132~14.04.1
  linux-image-generic-lts-xenial  4.4.0.109.92
  linux-image-lowlatency-lts-xenial  4.4.0.109.92

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

ATTENTION: Due to an unavoidable ABI change the kernel updates have
been given a new version number, which requires you to recompile and
reinstall all third party kernel modules you might have installed.
Unless you manually uninstalled the standard kernel metapackages
(e.g. linux-generic, linux-generic-lts-RELEASE, linux-virtual,
linux-powerpc), a standard system upgrade will automatically perform
this as well.

References:
  https://www.ubuntu.com/usn/usn-3522-4
  https://www.ubuntu.com/usn/usn-3522-1
  https://launchpad.net/bugs/1741934, https://usn.ubuntu.com/usn/usn-3522-2

Package Information:
  https://launchpad.net/ubuntu/+source/linux-lts-xenial/4.4.0-109.132~14.04.1

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