A Linux kernel security update has been released for Ubuntu 14.04 ESM, 16.04 ESM, and 18.04.

USN-5094-1: Linux kernel vulnerabilities

=========================================================================
Ubuntu Security Notice USN-5094-1
September 29, 2021

linux, linux-aws, linux-aws-hwe, linux-azure, linux-azure-4.15,
linux-dell300x, linux-gcp, linux-gcp-4.15, linux-hwe, linux-kvm,
linux-oracle, linux-snapdragon vulnerabilities
=========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 18.04 LTS
- Ubuntu 16.04 ESM
- 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-azure-4.15: Linux kernel for Microsoft Azure Cloud systems
- linux-dell300x: Linux kernel for Dell 300x platforms
- linux-gcp-4.15: Linux kernel for Google Cloud Platform (GCP) systems
- linux-kvm: Linux kernel for cloud environments
- linux-oracle: Linux kernel for Oracle Cloud systems
- linux-snapdragon: Linux kernel for Qualcomm Snapdragon processors
- linux-aws-hwe: Linux kernel for Amazon Web Services (AWS-HWE) systems
- linux-azure: Linux kernel for Microsoft Azure Cloud systems
- linux-gcp: Linux kernel for Google Cloud Platform (GCP) systems
- linux-hwe: Linux hardware enablement (HWE) kernel

Details:

It was discovered that the KVM hypervisor implementation in the Linux
kernel did not properly perform reference counting in some situations,
leading to a use-after-free vulnerability. An attacker who could start and
control a VM could possibly use this to expose sensitive information or
execute arbitrary code. (CVE-2021-22543)

It was discovered that the tracing subsystem in the Linux kernel did not
properly keep track of per-cpu ring buffer state. A privileged attacker
could use this to cause a denial of service. (CVE-2021-3679)

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)

Alexey Kardashevskiy discovered that the KVM implementation for PowerPC
systems in the Linux kernel did not properly validate RTAS arguments in
some situations. An attacker in a guest vm could use this to cause a denial
of service (host OS crash) or possibly execute arbitrary code.
(CVE-2021-37576)

It was discovered that the MAX-3421 host USB device driver in the Linux
kernel did not properly handle device removal events. A physically
proximate attacker could use this to cause a denial of service (system
crash). (CVE-2021-38204)

It was discovered that the Xilinx 10/100 Ethernet Lite device driver in the
Linux kernel could report pointer addresses in some situations. An attacker
could use this information to ease the exploitation of another
vulnerability. (CVE-2021-38205)

Update instructions:

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

Ubuntu 18.04 LTS:
linux-image-4.15.0-1028-dell300x 4.15.0-1028.33
linux-image-4.15.0-1081-oracle 4.15.0-1081.89
linux-image-4.15.0-1100-kvm 4.15.0-1100.102
linux-image-4.15.0-1109-gcp 4.15.0-1109.123
linux-image-4.15.0-1112-aws 4.15.0-1112.119
linux-image-4.15.0-1113-snapdragon 4.15.0-1113.122
linux-image-4.15.0-1124-azure 4.15.0-1124.137
linux-image-4.15.0-159-generic 4.15.0-159.167
linux-image-4.15.0-159-generic-lpae 4.15.0-159.167
linux-image-4.15.0-159-lowlatency 4.15.0-159.167
linux-image-aws-lts-18.04 4.15.0.1112.115
linux-image-azure-lts-18.04 4.15.0.1124.97
linux-image-dell300x 4.15.0.1028.30
linux-image-gcp-lts-18.04 4.15.0.1109.128
linux-image-generic 4.15.0.159.148
linux-image-generic-lpae 4.15.0.159.148
linux-image-kvm 4.15.0.1100.96
linux-image-lowlatency 4.15.0.159.148
linux-image-oracle-lts-18.04 4.15.0.1081.91
linux-image-snapdragon 4.15.0.1113.116
linux-image-virtual 4.15.0.159.148

Ubuntu 16.04 ESM:
linux-image-4.15.0-1081-oracle 4.15.0-1081.89~16.04.1
linux-image-4.15.0-1109-gcp 4.15.0-1109.123~16.04.1
linux-image-4.15.0-1112-aws 4.15.0-1112.119~16.04.1
linux-image-4.15.0-1124-azure 4.15.0-1124.137~16.04.1
linux-image-4.15.0-159-generic 4.15.0-159.167~16.04.1
linux-image-4.15.0-159-lowlatency 4.15.0-159.167~16.04.1
linux-image-aws-hwe 4.15.0.1112.103
linux-image-azure 4.15.0.1124.115
linux-image-gcp 4.15.0.1109.110
linux-image-generic-hwe-16.04 4.15.0.159.152
linux-image-gke 4.15.0.1109.110
linux-image-lowlatency-hwe-16.04 4.15.0.159.152
linux-image-oem 4.15.0.159.152
linux-image-oracle 4.15.0.1081.69
linux-image-virtual-hwe-16.04 4.15.0.159.152

Ubuntu 14.04 ESM:
linux-image-4.15.0-1124-azure 4.15.0-1124.137~14.04.1
linux-image-azure 4.15.0.1124.97

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-5094-1
CVE-2021-22543, CVE-2021-3679, CVE-2021-3732, CVE-2021-37576,
CVE-2021-38204, CVE-2021-38205

Package Information:
  https://launchpad.net/ubuntu/+source/linux/4.15.0-159.167
  https://launchpad.net/ubuntu/+source/linux-aws/4.15.0-1112.119
  https://launchpad.net/ubuntu/+source/linux-azure-4.15/4.15.0-1124.137
  https://launchpad.net/ubuntu/+source/linux-dell300x/4.15.0-1028.33
  https://launchpad.net/ubuntu/+source/linux-gcp-4.15/4.15.0-1109.123
  https://launchpad.net/ubuntu/+source/linux-kvm/4.15.0-1100.102
  https://launchpad.net/ubuntu/+source/linux-oracle/4.15.0-1081.89
  https://launchpad.net/ubuntu/+source/linux-snapdragon/4.15.0-1113.122