USN-3740-1: Linux kernel vulnerabilities

14 August 2018

linux, linux-aws, linux-azure, linux-gcp, linux-kvm, linux-oem, 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-aws - Linux kernel for Amazon Web Services (AWS) systems
  • linux-azure - Linux kernel for Microsoft Azure Cloud systems
  • linux-gcp - Linux kernel for Google Cloud Platform (GCP) systems
  • linux-kvm - Linux kernel for cloud environments
  • linux-oem - Linux kernel for OEM processors
  • linux-raspi2 - Linux kernel for Raspberry Pi 2

Details

It was discovered that memory present in the L1 data cache of an Intel CPU core may be exposed to a malicious process that is executing on the CPU core. This vulnerability is also known as L1 Terminal Fault (L1TF). A local attacker in a guest virtual machine could use this to expose sensitive information (memory from other guests or the host OS). (CVE-2018-3646)

It was discovered that memory present in the L1 data cache of an Intel CPU core may be exposed to a malicious process that is executing on the CPU core. This vulnerability is also known as L1 Terminal Fault (L1TF). A local attacker could use this to expose sensitive information (memory from the kernel or other processes). (CVE-2018-3620)

Juha-Matti Tilli discovered that the IP implementation in the Linux kernel performed algorithmically expensive operations in some situations when handling incoming packet fragments. A remote attacker could use this to cause a denial of service. (CVE-2018-5391)

Update instructions

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

Ubuntu 18.04 LTS
linux-image-4.15.0-1015-oem - 4.15.0.1015.17
linux-image-4.15.0-1017-gcp - 4.15.0-1017.18
linux-image-4.15.0-1019-aws - 4.15.0-1019.19
linux-image-4.15.0-1019-kvm - 4.15.0-1019.19
linux-image-4.15.0-1020-raspi2 - 4.15.0-1020.22
linux-image-4.15.0-1021-azure - 4.15.0.1021.21
linux-image-4.15.0-32-generic - 4.15.0-32.35
linux-image-4.15.0-32-generic-lpae - 4.15.0-32.35
linux-image-4.15.0-32-lowlatency - 4.15.0-32.35
linux-image-4.15.0-32-snapdragon - 4.15.0-32.35
linux-image-aws - 4.15.0.1019.19
linux-image-azure - 4.15.0.1021.21
linux-image-azure-edge - 4.15.0.1021.21
linux-image-gcp - 4.15.0.1017.19
linux-image-generic - 4.15.0.32.34
linux-image-generic-lpae - 4.15.0.32.34
linux-image-gke - 4.15.0.1017.19
linux-image-kvm - 4.15.0.1019.19
linux-image-lowlatency - 4.15.0.32.34
linux-image-oem - 4.15.0.1015.17
linux-image-raspi2 - 4.15.0.1020.18
linux-image-snapdragon - 4.15.0.32.34

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

Please note that the recommended mitigation for CVE-2018-3646 involves updating processor microcode in addition to updating the kernel; however, the kernel includes a fallback for processors that have not received microcode updates.

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