==========================================================================
Ubuntu Security Notice USN-4748-1
February 25, 2021

linux, linux-aws, linux-kvm, linux-lts-xenial, linux-raspi2,
linux-snapdragon vulnerabilities
==========================================================================

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

- Ubuntu 16.04 LTS
- Ubuntu 14.04 ESM

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-kvm: Linux kernel for cloud environments
- linux-raspi2: Linux kernel for Raspberry Pi (V8) systems
- linux-snapdragon: Linux kernel for Qualcomm Snapdragon processors
- linux-lts-xenial: Linux hardware enablement kernel from Xenial for Trusty

Details:

It was discovered that the jfs file system implementation in the Linux
kernel contained an out-of-bounds read vulnerability. A local attacker
could use this to possibly cause a denial of service (system crash).
(CVE-2020-27815)

It was discovered that the memory management subsystem in the Linux kernel
did not properly handle copy-on-write operations in some situations. A
local attacker could possibly use this to gain unintended write access to
read-only memory pages. (CVE-2020-29374)

Michael Kurth and Pawel Wieczorkiewicz discovered that the Xen event
processing backend in the Linux kernel did not properly limit the number of
events queued. An attacker in a guest VM could use this to cause a denial
of service in the host OS. (CVE-2020-29568)

Jann Horn discovered that the tty subsystem of the Linux kernel did not use
consistent locking in some situations, leading to a read-after-free
vulnerability. A local attacker could use this to cause a denial of service
(system crash) or possibly expose sensitive information (kernel memory).
(CVE-2020-29660)

Jann Horn discovered a race condition in the tty subsystem of the Linux
kernel in the locking for the TIOCSPGRP ioctl(), leading to a use-after-
free vulnerability. A local attacker could use this to cause a denial of
service (system crash) or possibly execute arbitrary code. (CVE-2020-29661)

Update instructions:

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

Ubuntu 16.04 LTS:
  linux-image-4.4.0-1088-kvm      4.4.0-1088.97
  linux-image-4.4.0-1122-aws      4.4.0-1122.136
  linux-image-4.4.0-1146-raspi2   4.4.0-1146.156
  linux-image-4.4.0-1150-snapdragon  4.4.0-1150.160
  linux-image-4.4.0-203-generic   4.4.0-203.235
  linux-image-4.4.0-203-generic-lpae  4.4.0-203.235
  linux-image-4.4.0-203-lowlatency  4.4.0-203.235
  linux-image-4.4.0-203-powerpc-e500mc  4.4.0-203.235
  linux-image-4.4.0-203-powerpc-smp  4.4.0-203.235
  linux-image-4.4.0-203-powerpc64-emb  4.4.0-203.235
  linux-image-4.4.0-203-powerpc64-smp  4.4.0-203.235
  linux-image-aws                 4.4.0.1122.127
  linux-image-generic             4.4.0.203.209
  linux-image-generic-lpae        4.4.0.203.209
  linux-image-kvm                 4.4.0.1088.86
  linux-image-lowlatency          4.4.0.203.209
  linux-image-powerpc-e500mc      4.4.0.203.209
  linux-image-powerpc-smp         4.4.0.203.209
  linux-image-powerpc64-emb       4.4.0.203.209
  linux-image-powerpc64-smp       4.4.0.203.209
  linux-image-raspi2              4.4.0.1146.146
  linux-image-snapdragon          4.4.0.1150.142
  linux-image-virtual             4.4.0.203.209

Ubuntu 14.04 ESM:
  linux-image-4.4.0-1086-aws      4.4.0-1086.90
  linux-image-4.4.0-203-generic   4.4.0-203.235~14.04.1
  linux-image-4.4.0-203-generic-lpae  4.4.0-203.235~14.04.1
  linux-image-4.4.0-203-lowlatency  4.4.0-203.235~14.04.1
  linux-image-4.4.0-203-powerpc-e500mc  4.4.0-203.235~14.04.1
  linux-image-4.4.0-203-powerpc-smp  4.4.0-203.235~14.04.1
  linux-image-4.4.0-203-powerpc64-emb  4.4.0-203.235~14.04.1
  linux-image-4.4.0-203-powerpc64-smp  4.4.0-203.235~14.04.1
  linux-image-aws                 4.4.0.1086.83
  linux-image-generic-lpae-lts-xenial  4.4.0.203.177
  linux-image-generic-lts-xenial  4.4.0.203.177
  linux-image-lowlatency-lts-xenial  4.4.0.203.177
  linux-image-powerpc-e500mc-lts-xenial  4.4.0.203.177
  linux-image-powerpc-smp-lts-xenial  4.4.0.203.177
  linux-image-powerpc64-emb-lts-xenial  4.4.0.203.177
  linux-image-powerpc64-smp-lts-xenial  4.4.0.203.177
  linux-image-virtual-lts-xenial  4.4.0.203.177

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://usn.ubuntu.com/4748-1
  CVE-2020-27815, CVE-2020-29374, CVE-2020-29568, CVE-2020-29660,
  CVE-2020-29661

Package Information:
  https://launchpad.net/ubuntu/+source/linux/4.4.0-203.235
  https://launchpad.net/ubuntu/+source/linux-aws/4.4.0-1122.136
  https://launchpad.net/ubuntu/+source/linux-kvm/4.4.0-1088.97
  https://launchpad.net/ubuntu/+source/linux-raspi2/4.4.0-1146.156
  https://launchpad.net/ubuntu/+source/linux-snapdragon/4.4.0-1150.160