USN-3836-1: Linux kernel vulnerabilities

3 December 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

To update your system, please follow these instructions: https://wiki.ubuntu.com/Security/Upgrades.

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