USN-3878-3: Linux kernel regression

8 February 2019

linux, linux-hwe regression

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

  • Ubuntu 18.10
  • Ubuntu 18.04 LTS

Summary

USN-3878-1 introduced a regression in the Linux kernel.

Software Description

  • linux - Linux kernel
  • linux-hwe - Linux hardware enablement (HWE) kernel

Details

USN-3878-1 fixed vulnerabilities in the Linux kernel. Unfortunately, that update introduced a regression that could prevent systems with certain graphics chipsets from booting. This update fixes the problem.

We apologize for the inconvenience.

Original advisory details:

It was discovered that a race condition existed in the vsock address family implementation of the Linux kernel that could lead to a use-after-free condition. A local attacker in a guest virtual machine could use this to expose sensitive information (host machine kernel memory). (CVE-2018-14625)

Cfir Cohen discovered that a use-after-free vulnerability existed in the KVM implementation of the Linux kernel, when handling interrupts in environments where nested virtualization is in use (nested KVM virtualization is not enabled by default in Ubuntu kernels). A local attacker in a guest VM could possibly use this to gain administrative privileges in a host machine. (CVE-2018-16882)

Wei Wu discovered that the KVM implementation in the Linux kernel did not properly ensure that ioapics were initialized. A local attacker could use this to cause a denial of service (system crash). (CVE-2018-19407)

It was discovered that the crypto subsystem of the Linux kernel leaked uninitialized memory to user space in some situations. A local attacker could use this to expose sensitive information (kernel memory). (CVE-2018-19854)

Update instructions

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

Ubuntu 18.10
linux-image-4.18.0-15-generic - 4.18.0-15.16
linux-image-4.18.0-15-generic-lpae - 4.18.0-15.16
linux-image-4.18.0-15-lowlatency - 4.18.0-15.16
linux-image-4.18.0-15-snapdragon - 4.18.0-15.16
linux-image-generic - 4.18.0.15.16
linux-image-generic-lpae - 4.18.0.15.16
linux-image-lowlatency - 4.18.0.15.16
linux-image-snapdragon - 4.18.0.15.16
Ubuntu 18.04 LTS
linux-image-4.18.0-15-generic - 4.18.0-15.16~18.04.1
linux-image-4.18.0-15-generic-lpae - 4.18.0-15.16~18.04.1
linux-image-4.18.0-15-lowlatency - 4.18.0-15.16~18.04.1
linux-image-4.18.0-15-snapdragon - 4.18.0-15.16~18.04.1
linux-image-generic-hwe-18.04 - 4.18.0.15.65
linux-image-generic-lpae-hwe-18.04 - 4.18.0.15.65
linux-image-lowlatency-hwe-18.04 - 4.18.0.15.65
linux-image-snapdragon-hwe-18.04 - 4.18.0.15.65

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