==========================================================================
Ubuntu Security Notice USN-6221-1
July 12, 2023

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

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

- Ubuntu 16.04 LTS (Available with Ubuntu Pro)
- Ubuntu 14.04 LTS (Available with Ubuntu Pro)

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-lts-xenial: Linux hardware enablement kernel from Xenial for Trusty

Details:

It was discovered that a race condition existed in the overlay file system
implementation in the Linux kernel. A local attacker could use this to
cause a denial of service (system crash). (CVE-2021-20321)

It was discovered that the virtual terminal (vt) device implementation in
the Linux kernel contained a race condition in its ioctl handling that led
to an out-of-bounds read vulnerability. A local attacker could possibly use
this to expose sensitive information. (CVE-2021-3753)

It was discovered that the ext4 file system implementation in the Linux
kernel contained a use-after-free vulnerability. An attacker could use this
to construct a malicious ext4 file system image that, when mounted, could
cause a denial of service (system crash). (CVE-2022-1184)

Pawan Kumar Gupta, Alyssa Milburn, Amit Peled, Shani Rehana, Nir Shildan
and Ariel Sabba discovered that some Intel processors with Enhanced
Indirect Branch Restricted Speculation (eIBRS) did not properly handle RET
instructions after a VM exits. A local attacker could potentially use this
to expose sensitive information. (CVE-2022-26373)

Johannes Wikner and Kaveh Razavi discovered that for some Intel x86-64
processors, the Linux kernel's protections against speculative branch
target injection attacks were insufficient in some circumstances. A local
attacker could possibly use this to expose sensitive information.
(CVE-2022-29901)

It was discovered that the ST NCI NFC driver did not properly handle device
removal events. A physically proximate attacker could use this to cause a
denial of service (system crash). (CVE-2023-1990)

It was discovered that the btrfs file system implementation in the Linux
kernel did not properly handle error conditions in some situations, leading
to a use-after-free vulnerability. A local attacker could possibly use this
to cause a denial of service (system crash). (CVE-2023-3111)

Update instructions:

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

Ubuntu 16.04 LTS (Available with Ubuntu Pro):
   linux-image-4.4.0-1121-kvm      4.4.0-1121.131
   linux-image-4.4.0-1158-aws      4.4.0-1158.173
   linux-image-4.4.0-242-generic   4.4.0-242.276
   linux-image-4.4.0-242-lowlatency  4.4.0-242.276
   linux-image-aws                 4.4.0.1158.162
   linux-image-generic             4.4.0.242.248
   linux-image-generic-lts-xenial  4.4.0.242.248
   linux-image-kvm                 4.4.0.1121.118
   linux-image-lowlatency          4.4.0.242.248
   linux-image-lowlatency-lts-xenial  4.4.0.242.248
   linux-image-virtual             4.4.0.242.248
   linux-image-virtual-lts-xenial  4.4.0.242.248

Ubuntu 14.04 LTS (Available with Ubuntu Pro):
   linux-image-4.4.0-1120-aws      4.4.0-1120.126
   linux-image-4.4.0-242-generic   4.4.0-242.276~14.04.1
   linux-image-4.4.0-242-lowlatency  4.4.0-242.276~14.04.1
   linux-image-aws                 4.4.0.1120.117
   linux-image-generic-lts-xenial  4.4.0.242.210
   linux-image-lowlatency-lts-xenial  4.4.0.242.210
   linux-image-virtual-lts-xenial  4.4.0.242.210

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-6221-1
   CVE-2021-20321, CVE-2021-3753, CVE-2022-1184, CVE-2022-26373,
   CVE-2022-29901, CVE-2023-1990, CVE-2023-3111