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

USN-5071-1: Linux kernel vulnerabilities

=========================================================================
Ubuntu Security Notice USN-5071-1
September 08, 2021

linux, linux-aws, linux-aws-5.4, linux-azure, linux-azure-5.4, linux-gcp,
linux-gcp-5.4, linux-gke, linux-gke-5.4, linux-gkeop, linux-gkeop-5.4,
linux-kvm, linux-oracle, linux-oracle-5.4 vulnerabilities
=========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 20.04 LTS
- Ubuntu 18.04 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-gke: Linux kernel for Google Container Engine (GKE) systems
- linux-gkeop: Linux kernel for Google Container Engine (GKE) systems
- linux-kvm: Linux kernel for cloud environments
- linux-oracle: Linux kernel for Oracle Cloud systems
- linux-aws-5.4: Linux kernel for Amazon Web Services (AWS) systems
- linux-azure-5.4: Linux kernel for Microsoft Azure cloud systems
- linux-gcp-5.4: Linux kernel for Google Cloud Platform (GCP) systems
- linux-gke-5.4: Linux kernel for Google Container Engine (GKE) systems
- linux-gkeop-5.4: Linux kernel for Google Container Engine (GKE) systems
- linux-oracle-5.4: Linux kernel for Oracle Cloud systems

Details:

Maxim Levitsky and Paolo Bonzini discovered that the KVM hypervisor
implementation for AMD processors in the Linux kernel allowed a guest VM to
disable restrictions on VMLOAD/VMSAVE in a nested guest. An attacker in a
guest VM could use this to read or write portions of the host's physical
memory. (CVE-2021-3656)

Maxim Levitsky discovered that the KVM hypervisor implementation for AMD
processors in the Linux kernel did not properly prevent a guest VM from
enabling AVIC in nested guest VMs. An attacker in a guest VM could use this
to write to portions of the host's physical memory. (CVE-2021-3653)

It was discovered that the KVM hypervisor implementation for AMD processors
in the Linux kernel did not ensure enough processing time was given to
perform cleanups of large SEV VMs. A local attacker could use this to cause
a denial of service (soft lockup). (CVE-2020-36311)

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)

Murray McAllister discovered that the joystick device interface in the
Linux kernel did not properly validate data passed via an ioctl(). A local
attacker could use this to cause a denial of service (system crash) or
possibly execute arbitrary code on systems with a joystick device
registered. (CVE-2021-3612)

Update instructions:

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

Ubuntu 20.04 LTS:
linux-image-5.4.0-1023-gkeop 5.4.0-1023.24
linux-image-5.4.0-1046-kvm 5.4.0-1046.48
linux-image-5.4.0-1052-gcp 5.4.0-1052.56
linux-image-5.4.0-1052-gke 5.4.0-1052.55
linux-image-5.4.0-1054-oracle 5.4.0-1054.58
linux-image-5.4.0-1056-aws 5.4.0-1056.59
linux-image-5.4.0-1058-azure 5.4.0-1058.60
linux-image-5.4.0-84-generic 5.4.0-84.94
linux-image-5.4.0-84-generic-lpae 5.4.0-84.94
linux-image-5.4.0-84-lowlatency 5.4.0-84.94
linux-image-aws-lts-20.04 5.4.0.1056.59
linux-image-azure-lts-20.04 5.4.0.1058.56
linux-image-gcp-lts-20.04 5.4.0.1052.62
linux-image-generic 5.4.0.84.88
linux-image-generic-lpae 5.4.0.84.88
linux-image-gke 5.4.0.1052.62
linux-image-gke-5.4 5.4.0.1052.62
linux-image-gkeop 5.4.0.1023.26
linux-image-gkeop-5.4 5.4.0.1023.26
linux-image-kvm 5.4.0.1046.45
linux-image-lowlatency 5.4.0.84.88
linux-image-oem 5.4.0.84.88
linux-image-oem-osp1 5.4.0.84.88
linux-image-oracle-lts-20.04 5.4.0.1054.54
linux-image-virtual 5.4.0.84.88

Ubuntu 18.04 LTS:
linux-image-5.4.0-1023-gkeop 5.4.0-1023.24~18.04.1
linux-image-5.4.0-1052-gcp 5.4.0-1052.56~18.04.1
linux-image-5.4.0-1052-gke 5.4.0-1052.55~18.04.1
linux-image-5.4.0-1054-oracle 5.4.0-1054.58~18.04.1
linux-image-5.4.0-1056-aws 5.4.0-1056.59~18.04.1
linux-image-5.4.0-1058-azure 5.4.0-1058.60~18.04.1
linux-image-aws 5.4.0.1056.39
linux-image-azure 5.4.0.1058.38
linux-image-gcp 5.4.0.1052.38
linux-image-gke-5.4 5.4.0.1052.55~18.04.17
linux-image-gkeop-5.4 5.4.0.1023.24~18.04.24
linux-image-oracle 5.4.0.1054.58~18.04.34

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-5071-1
CVE-2020-36311, CVE-2021-22543, CVE-2021-3612, CVE-2021-3653,
CVE-2021-3656

Package Information:
  https://launchpad.net/ubuntu/+source/linux/5.4.0-84.94
  https://launchpad.net/ubuntu/+source/linux-aws/5.4.0-1056.59
  https://launchpad.net/ubuntu/+source/linux-azure/5.4.0-1058.60
  https://launchpad.net/ubuntu/+source/linux-gcp/5.4.0-1052.56
  https://launchpad.net/ubuntu/+source/linux-gke/5.4.0-1052.55
  https://launchpad.net/ubuntu/+source/linux-gkeop/5.4.0-1023.24
  https://launchpad.net/ubuntu/+source/linux-kvm/5.4.0-1046.48
  https://launchpad.net/ubuntu/+source/linux-oracle/5.4.0-1054.58
  https://launchpad.net/ubuntu/+source/linux-aws-5.4/5.4.0-1056.59~18.04.1
  https://launchpad.net/ubuntu/+source/linux-azure-5.4/5.4.0-1058.60~18.04.1
  https://launchpad.net/ubuntu/+source/linux-gcp-5.4/5.4.0-1052.56~18.04.1
  https://launchpad.net/ubuntu/+source/linux-gke-5.4/5.4.0-1052.55~18.04.1
  https://launchpad.net/ubuntu/+source/linux-gkeop-5.4/5.4.0-1023.24~18.04.1
  https://launchpad.net/ubuntu/+source/linux-oracle-5.4/5.4.0-1054.58~18.04.1

--VnSgjHU/LbyONhNn