A Linux kernel security update has been released for Ubuntu Linux 21.04, 20.04 LTS, 18.04 LTS, and 16.04 ESM.

USN-5086-1: Linux kernel vulnerability

=========================================================================
Ubuntu Security Notice USN-5086-1
September 22, 2021

linux, linux-hwe, linux-hwe-5.11, linux-hwe-5.4 vulnerability
=========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 21.04
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 ESM

Summary:

IBM s390x systems could be made to crash or run programs as an
administrator.

Software Description:
- linux: Linux kernel
- linux-hwe-5.11: Linux hardware enablement (HWE) kernel
- linux-hwe-5.4: Linux hardware enablement (HWE) kernel
- linux-hwe: Linux hardware enablement (HWE) kernel

Details:

Johan Almbladh discovered that the eBPF JIT implementation for IBM
s390x systems in the Linux kernel miscompiled operations in some
situations, allowing circumvention of the BPF verifier. A local
attacker could use this to cause a denial of service (system crash)
or possibly execute arbitrary code.

Update instructions:

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

Ubuntu 21.04:
linux-image-5.11.0-36-generic 5.11.0-36.40
linux-image-5.11.0-36-generic-64k 5.11.0-36.40
linux-image-5.11.0-36-generic-lpae 5.11.0-36.40
linux-image-5.11.0-36-lowlatency 5.11.0-36.40
linux-image-generic 5.11.0.36.38
linux-image-generic-64k 5.11.0.36.38
linux-image-generic-lpae 5.11.0.36.38
linux-image-lowlatency 5.11.0.36.38
linux-image-oem-20.04 5.11.0.36.38
linux-image-virtual 5.11.0.36.38

Ubuntu 20.04 LTS:
linux-image-5.11.0-36-generic 5.11.0-36.40~20.04.1
linux-image-5.11.0-36-generic-64k 5.11.0-36.40~20.04.1
linux-image-5.11.0-36-generic-lpae 5.11.0-36.40~20.04.1
linux-image-5.11.0-36-lowlatency 5.11.0-36.40~20.04.1
linux-image-5.4.0-86-generic 5.4.0-86.97
linux-image-5.4.0-86-generic-lpae 5.4.0-86.97
linux-image-5.4.0-86-lowlatency 5.4.0-86.97
linux-image-generic 5.4.0.86.90
linux-image-generic-64k-hwe-20.04 5.11.0.36.40~20.04.15
linux-image-generic-hwe-20.04 5.11.0.36.40~20.04.15
linux-image-generic-lpae 5.4.0.86.90
linux-image-generic-lpae-hwe-20.04 5.11.0.36.40~20.04.15
linux-image-lowlatency 5.4.0.86.90
linux-image-lowlatency-hwe-20.04 5.11.0.36.40~20.04.15
linux-image-oem 5.4.0.86.90
linux-image-oem-osp1 5.4.0.86.90
linux-image-virtual 5.4.0.86.90
linux-image-virtual-hwe-20.04 5.11.0.36.40~20.04.15

Ubuntu 18.04 LTS:
linux-image-4.15.0-158-generic 4.15.0-158.166
linux-image-4.15.0-158-generic-lpae 4.15.0-158.166
linux-image-4.15.0-158-lowlatency 4.15.0-158.166
linux-image-5.4.0-86-generic 5.4.0-86.97~18.04.1
linux-image-5.4.0-86-generic-lpae 5.4.0-86.97~18.04.1
linux-image-5.4.0-86-lowlatency 5.4.0-86.97~18.04.1
linux-image-generic 4.15.0.158.147
linux-image-generic-hwe-18.04 5.4.0.86.97~18.04.77
linux-image-generic-lpae 4.15.0.158.147
linux-image-generic-lpae-hwe-18.04 5.4.0.86.97~18.04.77
linux-image-lowlatency 4.15.0.158.147
linux-image-lowlatency-hwe-18.04 5.4.0.86.97~18.04.77
linux-image-oem 5.4.0.86.97~18.04.77
linux-image-oem-osp1 5.4.0.86.97~18.04.77
linux-image-snapdragon-hwe-18.04 5.4.0.86.97~18.04.77
linux-image-virtual 4.15.0.158.147
linux-image-virtual-hwe-18.04 5.4.0.86.97~18.04.77

Ubuntu 16.04 ESM:
linux-image-4.15.0-158-generic 4.15.0-158.166~16.04.1
linux-image-4.15.0-158-lowlatency 4.15.0-158.166~16.04.1
linux-image-4.4.0-216-generic 4.4.0-216.249
linux-image-4.4.0-216-lowlatency 4.4.0-216.249
linux-image-generic 4.4.0.216.223
linux-image-generic-hwe-16.04 4.15.0.158.151
linux-image-lowlatency 4.4.0.216.223
linux-image-lowlatency-hwe-16.04 4.15.0.158.151
linux-image-oem 4.15.0.158.151
linux-image-virtual 4.4.0.216.223
linux-image-virtual-hwe-16.04 4.15.0.158.151

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-5086-1
https://launchpad.net/bugs/1943960

Package Information:
https://launchpad.net/ubuntu/+source/linux/5.11.0-36.40
https://launchpad.net/ubuntu/+source/linux/5.4.0-86.97
https://launchpad.net/ubuntu/+source/linux-hwe-5.11/5.11.0-36.40~20.04.1
https://launchpad.net/ubuntu/+source/linux/4.15.0-158.166
https://launchpad.net/ubuntu/+source/linux-hwe-5.4/5.4.0-86.97~18.04.1