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

LSN-0082-1: Linux kernel vulnerability

Linux kernel vulnerabilities

A security issue affects these releases of Ubuntu and its derivatives:
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 ESM

Summary

Several security issues were fixed in the kernel.

Software Description

- linux - Linux kernel
- linux-gcp - Linux kernel for Google Cloud Platform (GCP) systems - linux-gke - Linux kernel for Google Container Engine (GKE) systems - linux-gkeop - Linux kernel for Google Container Engine (GKE) systems - linux-oem - Linux kernel for OEM systems

Details

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)

De4dCr0w of 360 Alpha Lab discovered that the BPF verifier in the Linux kernel did not properly handle mod32 destination register truncation when the source register was known to be 0. A local attacker could use this to expose sensitive information (kernel memory) or possibly execute arbitrary code. (CVE-2021-3444)

kernel: use-after-free in route4_change() in net/sched/cls_route.c (CVE-2021-3715)

Update instructions

The problem can be corrected by updating your kernel livepatch to the following versions:

Ubuntu 20.04 LTS
gcp - 82.2
generic - 82.2
gke - 82.2
gkeop - 82.2
lowlatency - 82.2

Ubuntu 18.04 LTS
generic - 82.1
generic - 82.2
gke - 82.1
gke - 82.2
gkeop - 82.2
lowlatency - 82.1
lowlatency - 82.2
oem - 82.1
oem - 82.2

Ubuntu 16.04 ESM
generic - 82.1
generic - 82.2
lowlatency - 82.1
lowlatency - 82.2

Support Information

Kernels older than the levels listed below do not receive livepatch updates. If you are running a kernel version earlier than the one listed below, please upgrade your kernel as soon as possible.

Ubuntu 20.04 LTS
linux-aws - 5.4.0-1009
linux-azure - 5.4.0-1010
linux-gcp - 5.4.0-1009
linux-gke - 5.4.0-1033
linux-gkeop - 5.4.0-1009
linux-oem - 5.4.0-26
linux - 5.4.0-26

Ubuntu 18.04 LTS
linux-aws - 4.15.0-1054
linux-azure-4.15 - 4.15.0-1115
linux-gke-4.15 - 4.15.0-1076
linux-gke-5.4 - 5.4.0-1009
linux-gkeop-5.4 - 5.4.0-1007
linux-hwe-5.4 - 5.4.0-26
linux-oem - 4.15.0-1063
linux - 4.15.0-69

Ubuntu 16.04 ESM
linux-aws - 4.4.0-1098
linux-azure - 4.15.0-1063
linux-hwe - 4.15.0-69
linux - 4.4.0-168

Ubuntu 14.04 ESM
linux-lts-xenial - 4.4.0-168

References

- CVE-2020-29660
- CVE-2020-29661
- CVE-2021-3444
- CVE-2021-3715