USN-3777-1: Linux kernel vulnerabilities

1 October 2018

linux, linux-aws, 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-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

Jann Horn discovered that the vmacache subsystem did not properly handle sequence number overflows, leading to a use-after-free vulnerability. A local attacker could use this to cause a denial of service (system crash) or execute arbitrary code. (CVE-2018-17182)

It was discovered that the paravirtualization implementation in the Linux kernel did not properly handle some indirect calls, reducing the effectiveness of Spectre v2 mitigations for paravirtual guests. A local attacker could use this to expose sensitive information. (CVE-2018-15594)

It was discovered that microprocessors utilizing speculative execution and prediction of return addresses via Return Stack Buffer (RSB) may allow unauthorized memory reads via sidechannel attacks. An attacker could use this to expose sensitive information. (CVE-2018-15572)

Andy Lutomirski and Mika Penttilä discovered that the KVM implementation in the Linux kernel did not properly check privilege levels when emulating some instructions. An unprivileged attacker in a guest VM could use this to escalate privileges within the guest. (CVE-2018-10853)

It was discovered that a stack-based buffer overflow existed in the iSCSI target implementation of the Linux kernel. A remote attacker could use this to cause a denial of service (system crash). (CVE-2018-14633)

It was discovered that a memory leak existed in the IRDA subsystem of the Linux kernel. A local attacker could use this to cause a denial of service (kernel memory exhaustion). (CVE-2018-6554)

It was discovered that a use-after-free vulnerability existed in the IRDA implementation in the Linux kernel. A local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code. (CVE-2018-6555)

USN 3652-1 added a mitigation for Speculative Store Bypass a.k.a. Spectre Variant 4 (CVE-2018-3639). This update provides the corresponding mitigation for ARM64 processors. Please note that for this mitigation to be effective, an updated firmware for the processor may be required.

Update instructions

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

Ubuntu 18.04 LTS
linux-image-4.15.0-1021-gcp - 4.15.0-1021.22
linux-image-4.15.0-1021-oem - 4.15.0-1021.24
linux-image-4.15.0-1023-aws - 4.15.0-1023.23
linux-image-4.15.0-1023-kvm - 4.15.0-1023.23
linux-image-4.15.0-1024-raspi2 - 4.15.0-1024.26
linux-image-4.15.0-36-generic - 4.15.0-36.39
linux-image-4.15.0-36-generic-lpae - 4.15.0-36.39
linux-image-4.15.0-36-lowlatency - 4.15.0-36.39
linux-image-4.15.0-36-snapdragon - 4.15.0-36.39
linux-image-aws - 4.15.0.1023.23
linux-image-gcp - 4.15.0.1021.23
linux-image-generic - 4.15.0.36.38
linux-image-generic-lpae - 4.15.0.36.38
linux-image-gke - 4.15.0.1021.23
linux-image-kvm - 4.15.0.1023.23
linux-image-lowlatency - 4.15.0.36.38
linux-image-oem - 4.15.0.1021.23
linux-image-raspi2 - 4.15.0.1024.22
linux-image-snapdragon - 4.15.0.36.38

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