[USN-5062-1] Linux kernel vulnerability

[Steve Beattie]

==========================================================================
Ubuntu Security Notice USN-5062-1
September 08, 2021

linux, linux-aws, linux-kvm, linux-lts-xenial vulnerability
==========================================================================

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

- Ubuntu 16.04 ESM
- Ubuntu 14.04 ESM

Summary:

The system could be made to crash or run programs as an administrator.

Software Description:
- linux: Linux kernel
- linux-aws: Linux kernel for Amazon Web Services (AWS) systems
- linux-kvm: Linux kernel for cloud environments
- linux-lts-xenial: Linux hardware enablement kernel from Xenial for Trusty

Details:

Maxim Levitsky discovered that the KVM hypervisor implementation for AMD
processors in the Linux kernel did not properly prevent a guest VM from
enabling AVIC in nested guest VMs. An attacker in a guest VM could use this
to write to portions of the host's physical memory.

Update instructions:

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

Ubuntu 16.04 ESM:
  linux-image-4.4.0-1097-kvm      4.4.0-1097.106
  linux-image-4.4.0-1132-aws      4.4.0-1132.146
  linux-image-4.4.0-214-generic   4.4.0-214.246
  linux-image-4.4.0-214-lowlatency  4.4.0-214.246
  linux-image-aws                 4.4.0.1132.137
  linux-image-generic             4.4.0.214.221
  linux-image-kvm                 4.4.0.1097.95
  linux-image-lowlatency          4.4.0.214.221
  linux-image-virtual             4.4.0.214.221

Ubuntu 14.04 ESM:
  linux-image-4.4.0-1096-aws      4.4.0-1096.101
  linux-image-4.4.0-214-generic   4.4.0-214.246~14.04.1
  linux-image-4.4.0-214-lowlatency  4.4.0-214.246~14.04.1
  linux-image-aws                 4.4.0.1096.94
  linux-image-generic-lts-xenial  4.4.0.214.187
  linux-image-lowlatency-lts-xenial  4.4.0.214.187
  linux-image-virtual-lts-xenial  4.4.0.214.187

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:
  https://ubuntu.com/security/notices/USN-5062-1
  CVE-2021-3653

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