Ubuntu 18.04 LTS USN-3836-1 Critical: Kernel Access Control Fix

ubuntu

December 3, 2018

Several security issues were fixed in the Linux kernel.

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)

Topics Covered

security advisory update critical access control kernel ubuntu linux-image

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.