==========================================================================
Ubuntu Security Notice USN-5211-1
January 06, 2022

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:

Nadav Amit discovered that the hugetlb implementation in the Linux kernel
did not perform TLB flushes under certain conditions. A local attacker
could use this to leak or alter data from other processes that use huge
pages.

Update instructions:

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

Ubuntu 16.04 ESM:
  linux-image-4.4.0-1099-kvm      4.4.0-1099.108
  linux-image-4.4.0-1134-aws      4.4.0-1134.148
  linux-image-4.4.0-218-generic   4.4.0-218.251
  linux-image-4.4.0-218-lowlatency  4.4.0-218.251
  linux-image-aws                 4.4.0.1134.139
  linux-image-generic             4.4.0.218.225
  linux-image-kvm                 4.4.0.1099.97
  linux-image-lowlatency          4.4.0.218.225
  linux-image-virtual             4.4.0.218.225

Ubuntu 14.04 ESM:
  linux-image-3.13.0-189-generic  3.13.0-189.240
  linux-image-3.13.0-189-generic-lpae  3.13.0-189.240
  linux-image-3.13.0-189-lowlatency  3.13.0-189.240
  linux-image-4.4.0-1098-aws      4.4.0-1098.103
  linux-image-4.4.0-218-generic   4.4.0-218.251~14.04.1
  linux-image-4.4.0-218-lowlatency  4.4.0-218.251~14.04.1
  linux-image-aws                 4.4.0.1098.96
  linux-image-generic             3.13.0.189.198
  linux-image-generic-lpae        3.13.0.189.198
  linux-image-generic-lts-xenial  4.4.0.218.189
  linux-image-lowlatency          3.13.0.189.198
  linux-image-lowlatency-lts-xenial  4.4.0.218.189
  linux-image-server              3.13.0.189.198
  linux-image-virtual             3.13.0.189.198
  linux-image-virtual-lts-xenial  4.4.0.218.189

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-5211-1
  CVE-2021-4002