A Linux kernel security update has been released for Ubuntu Linux 20.04 LTS and 21.04.

USN-5113-1: Linux kernel vulnerabilities

=========================================================================
Ubuntu Security Notice USN-5113-1
October 19, 2021

linux, linux-aws, linux-aws-5.11, linux-azure, linux-azure-5.11,
linux-gcp, linux-gcp-5.11, linux-hwe-5.11, linux-kvm, linux-raspi
vulnerabilities
=========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 21.04
- Ubuntu 20.04 LTS

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-azure: Linux kernel for Microsoft Azure Cloud systems
- linux-gcp: Linux kernel for Google Cloud Platform (GCP) systems
- linux-kvm: Linux kernel for cloud environments
- linux-raspi: Linux kernel for Raspberry Pi systems
- linux-aws-5.11: Linux kernel for Amazon Web Services (AWS) systems
- linux-azure-5.11: Linux kernel for Microsoft Azure cloud systems
- linux-gcp-5.11: Linux kernel for Google Cloud Platform (GCP) systems
- linux-hwe-5.11: Linux hardware enablement (HWE) kernel

Details:

It was discovered that a race condition existed in the Atheros Ath9k WiFi
driver in the Linux kernel. An attacker could possibly use this to expose
sensitive information (WiFi network traffic). (CVE-2020-3702)

Alois Wohlschlager discovered that the overlay file system in the Linux
kernel did not restrict private clones in some situations. An attacker
could use this to expose sensitive information. (CVE-2021-3732)

It was discovered that the btrfs file system in the Linux kernel did not
properly handle removing a non-existent device id. An attacker with
CAP_SYS_ADMIN could use this to cause a denial of service. (CVE-2021-3739)

It was discovered that the Qualcomm IPC Router protocol implementation in
the Linux kernel did not properly validate metadata in some situations. A
local attacker could use this to cause a denial of service (system crash)
or expose sensitive information. (CVE-2021-3743)

It was discovered that the virtual terminal (vt) device implementation in
the Linux kernel contained a race condition in its ioctl handling that lead
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 BPF subsystem in the Linux kernel contained an
integer overflow in its hash table implementation. A local attacker could
use this to cause a denial of service (system crash) or possibly execute
arbitrary code. (CVE-2021-38166)

It was discovered that the ext4 file system in the Linux kernel contained a
race condition when writing xattrs to an inode. A local attacker could use
this to cause a denial of service or possibly gain administrative
privileges. (CVE-2021-40490)

It was discovered that the 6pack network protocol driver in the Linux
kernel did not properly perform validation checks. A privileged attacker
could use this to cause a denial of service (system crash) or execute
arbitrary code. (CVE-2021-42008)

Update instructions:

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

Ubuntu 21.04:
linux-image-5.11.0-1018-kvm 5.11.0-1018.19
linux-image-5.11.0-1020-aws 5.11.0-1020.21
linux-image-5.11.0-1020-azure 5.11.0-1020.21
linux-image-5.11.0-1021-gcp 5.11.0-1021.23
linux-image-5.11.0-1021-raspi 5.11.0-1021.22
linux-image-5.11.0-1021-raspi-nolpae 5.11.0-1021.22
linux-image-5.11.0-38-generic 5.11.0-38.42
linux-image-5.11.0-38-generic-64k 5.11.0-38.42
linux-image-5.11.0-38-generic-lpae 5.11.0-38.42
linux-image-5.11.0-38-lowlatency 5.11.0-38.42
linux-image-aws 5.11.0.1020.21
linux-image-azure 5.11.0.1020.21
linux-image-gcp 5.11.0.1021.21
linux-image-generic 5.11.0.38.39
linux-image-generic-64k 5.11.0.38.39
linux-image-generic-lpae 5.11.0.38.39
linux-image-gke 5.11.0.1021.21
linux-image-kvm 5.11.0.1018.19
linux-image-lowlatency 5.11.0.38.39
linux-image-oem-20.04 5.11.0.38.39
linux-image-raspi 5.11.0.1021.19
linux-image-raspi-nolpae 5.11.0.1021.19
linux-image-virtual 5.11.0.38.39

Ubuntu 20.04 LTS:
linux-image-5.11.0-1020-aws 5.11.0-1020.21~20.04.2
linux-image-5.11.0-1020-azure 5.11.0-1020.21~20.04.1
linux-image-5.11.0-1021-gcp 5.11.0-1021.23~20.04.1
linux-image-5.11.0-38-generic 5.11.0-38.42~20.04.1
linux-image-5.11.0-38-generic-64k 5.11.0-38.42~20.04.1
linux-image-5.11.0-38-generic-lpae 5.11.0-38.42~20.04.1
linux-image-5.11.0-38-lowlatency 5.11.0-38.42~20.04.1
linux-image-aws 5.11.0.1020.21~20.04.19
linux-image-azure-edge 5.11.0.1020.21~20.04.19
linux-image-gcp 5.11.0.1021.23~20.04.20
linux-image-generic-64k-hwe-20.04 5.11.0.38.42~20.04.17
linux-image-generic-hwe-20.04 5.11.0.38.42~20.04.17
linux-image-generic-lpae-hwe-20.04 5.11.0.38.42~20.04.17
linux-image-lowlatency-hwe-20.04 5.11.0.38.42~20.04.17
linux-image-virtual-hwe-20.04 5.11.0.38.42~20.04.17

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-5113-1
CVE-2020-3702, CVE-2021-3732, CVE-2021-3739, CVE-2021-3743,
CVE-2021-3753, CVE-2021-38166, CVE-2021-40490, CVE-2021-42008

Package Information:
  https://launchpad.net/ubuntu/+source/linux/5.11.0-38.42
  https://launchpad.net/ubuntu/+source/linux-aws/5.11.0-1020.21
  https://launchpad.net/ubuntu/+source/linux-azure/5.11.0-1020.21
  https://launchpad.net/ubuntu/+source/linux-gcp/5.11.0-1021.23
  https://launchpad.net/ubuntu/+source/linux-kvm/5.11.0-1018.19
  https://launchpad.net/ubuntu/+source/linux-raspi/5.11.0-1021.22
  https://launchpad.net/ubuntu/+source/linux-aws-5.11/5.11.0-1020.21~20.04.2
  https://launchpad.net/ubuntu/+source/linux-azure-5.11/5.11.0-1020.21~20.04.1
  https://launchpad.net/ubuntu/+source/linux-gcp-5.11/5.11.0-1021.23~20.04.1
  https://launchpad.net/ubuntu/+source/linux-hwe-5.11/5.11.0-38.42~20.04.1