[USN-3836-1] Linux kernel vulnerabilities

[Steve Beattie]

==========================================================================
Ubuntu Security Notice USN-3836-1
December 03, 2018

linux, linux-gcp, linux-kvm, linux-raspi2 vulnerabilities
==========================================================================

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

- Ubuntu 18.04 LTS

Summary:

Several security issues were fixed in the Linux kernel.

Software Description:
- linux: Linux kernel
- linux-gcp: Linux kernel for Google Cloud Platform (GCP) systems
- linux-kvm: Linux kernel for cloud environments
- linux-raspi2: Linux kernel for Raspberry Pi 2

Details:

Jann Horn discovered that the Linux kernel mishandles mapping UID or GID
ranges inside nested user namespaces in some situations. A local attacker
could use this to bypass access controls on resources outside the
namespace. (CVE-2018-18955)

Philipp Wendler discovered that the overlayfs implementation in the Linux
kernel did not properly verify the directory contents permissions from
within a unprivileged user namespace. A local attacker could use this to
expose sensitive information (protected file names). (CVE-2018-6559)

Update instructions:

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

Ubuntu 18.04 LTS:
  linux-image-4.15.0-1025-gcp     4.15.0-1025.26
  linux-image-4.15.0-1027-kvm     4.15.0-1027.27
  linux-image-4.15.0-1029-raspi2  4.15.0-1029.31
  linux-image-4.15.0-42-generic   4.15.0-42.45
  linux-image-4.15.0-42-generic-lpae  4.15.0-42.45
  linux-image-4.15.0-42-lowlatency  4.15.0-42.45
  linux-image-4.15.0-42-snapdragon  4.15.0-42.45
  linux-image-gcp                 4.15.0.1025.27
  linux-image-generic             4.15.0.42.44
  linux-image-generic-lpae        4.15.0.42.44
  linux-image-gke                 4.15.0.1025.27
  linux-image-kvm                 4.15.0.1027.27
  linux-image-lowlatency          4.15.0.42.44
  linux-image-raspi2              4.15.0.1029.27
  linux-image-snapdragon          4.15.0.42.44

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://usn.ubuntu.com/usn/usn-3836-1
  CVE-2018-18955, CVE-2018-6559

Package Information:
  https://launchpad.net/ubuntu/+source/linux/4.15.0-42.45
  https://launchpad.net/ubuntu/+source/linux-gcp/4.15.0-1025.26
  https://launchpad.net/ubuntu/+source/linux-kvm/4.15.0-1027.27
  https://launchpad.net/ubuntu/+source/linux-raspi2/4.15.0-1029.31

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