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

USN-4679-1: Linux kernel vulnerabilities

==========================================================================
Ubuntu Security Notice USN-4679-1
January 06, 2021

linux, linux-aws, linux-aws-5.4, linux-azure, linux-azure-5.4, linux-gcp,
linux-gcp-5.4, linux-gke-5.4, linux-hwe-5.4, linux-kvm, linux-oracle,
linux-oracle-5.4, linux-raspi, linux-raspi-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-kvm: Linux kernel for cloud environments
- linux-oracle: Linux kernel for Oracle Cloud systems
- linux-raspi: Linux kernel for Raspberry Pi (V8) 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-hwe-5.4: Linux hardware enablement (HWE) kernel
- linux-oracle-5.4: Linux kernel for Oracle Cloud systems
- linux-raspi-5.4: Linux kernel for Raspberry Pi (V8) systems

Details:

It was discovered that the console keyboard driver in the Linux kernel
contained a race condition. A local attacker could use this to expose
sensitive information (kernel memory). (CVE-2020-25656)

Minh Yuan discovered that the tty driver in the Linux kernel contained race
conditions when handling fonts. A local attacker could possibly use this to
expose sensitive information (kernel memory). (CVE-2020-25668)

Kiyin (尹亮) discovered that the perf subsystem in the Linux kernel did
not properly deallocate memory in some situations. A privileged attacker
could use this to cause a denial of service (kernel memory exhaustion).
(CVE-2020-25704)

Jinoh Kang discovered that the Xen event channel infrastructure in the
Linux kernel contained a race condition. An attacker in guest could
possibly use this to cause a denial of service (dom0 crash).
(CVE-2020-27675)

Daniel Axtens discovered that PowerPC RTAS implementation in the Linux
kernel did not properly restrict memory accesses in some situations. A
privileged local attacker could use this to arbitrarily modify kernel
memory, potentially bypassing kernel lockdown restrictions.
(CVE-2020-27777)

Minh Yuan discovered that the framebuffer console driver in the Linux
kernel did not properly handle fonts in some conditions. A local attacker
could use this to cause a denial of service (system crash) or possibly
expose sensitive information (kernel memory). (CVE-2020-28974)

Update instructions:

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

Ubuntu 20.04 LTS:
linux-image-5.4.0-1026-raspi 5.4.0-1026.29
linux-image-5.4.0-1031-kvm 5.4.0-1031.32
linux-image-5.4.0-1033-gcp 5.4.0-1033.35
linux-image-5.4.0-1034-aws 5.4.0-1034.35
linux-image-5.4.0-1034-oracle 5.4.0-1034.36
linux-image-5.4.0-1035-azure 5.4.0-1035.36
linux-image-5.4.0-59-generic 5.4.0-59.65
linux-image-5.4.0-59-generic-lpae 5.4.0-59.65
linux-image-5.4.0-59-lowlatency 5.4.0-59.65
linux-image-aws 5.4.0.1034.35
linux-image-azure 5.4.0.1035.33
linux-image-gcp 5.4.0.1033.42
linux-image-generic 5.4.0.59.62
linux-image-generic-lpae 5.4.0.59.62
linux-image-kvm 5.4.0.1031.29
linux-image-lowlatency 5.4.0.59.62
linux-image-oem 5.4.0.59.62
linux-image-oem-osp1 5.4.0.59.62
linux-image-oracle 5.4.0.1034.31
linux-image-raspi 5.4.0.1026.61
linux-image-raspi2 5.4.0.1026.61
linux-image-virtual 5.4.0.59.62

Ubuntu 18.04 LTS:
linux-image-5.4.0-1026-raspi 5.4.0-1026.29~18.04.1
linux-image-5.4.0-1033-gcp 5.4.0-1033.35~18.04.1
linux-image-5.4.0-1033-gke 5.4.0-1033.35~18.04.1
linux-image-5.4.0-1034-aws 5.4.0-1034.35~18.04.1
linux-image-5.4.0-1034-oracle 5.4.0-1034.36~18.04.1
linux-image-5.4.0-1035-azure 5.4.0-1035.36~18.04.1
linux-image-5.4.0-59-generic 5.4.0-59.65~18.04.1
linux-image-5.4.0-59-generic-lpae 5.4.0-59.65~18.04.1
linux-image-5.4.0-59-lowlatency 5.4.0-59.65~18.04.1
linux-image-aws 5.4.0.1034.19
linux-image-azure 5.4.0.1035.17
linux-image-gcp 5.4.0.1033.21
linux-image-generic-hwe-18.04 5.4.0.59.65~18.04.54
linux-image-generic-lpae-hwe-18.04 5.4.0.59.65~18.04.54
linux-image-gke-5.4 5.4.0.1033.35~18.04.2
linux-image-lowlatency-hwe-18.04 5.4.0.59.65~18.04.54
linux-image-oem 5.4.0.59.65~18.04.54
linux-image-oem-osp1 5.4.0.59.65~18.04.54
linux-image-oracle 5.4.0.1034.36~18.04.18
linux-image-raspi-hwe-18.04 5.4.0.1026.30
linux-image-snapdragon-hwe-18.04 5.4.0.59.65~18.04.54
linux-image-virtual-hwe-18.04 5.4.0.59.65~18.04.54

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://usn.ubuntu.com/4679-1
CVE-2020-25656, CVE-2020-25668, CVE-2020-25704, CVE-2020-27675,
CVE-2020-27777, CVE-2020-28974

Package Information:
  https://launchpad.net/ubuntu/+source/linux/5.4.0-59.65
  https://launchpad.net/ubuntu/+source/linux-aws/5.4.0-1034.35
  https://launchpad.net/ubuntu/+source/linux-azure/5.4.0-1035.36
  https://launchpad.net/ubuntu/+source/linux-gcp/5.4.0-1033.35
  https://launchpad.net/ubuntu/+source/linux-kvm/5.4.0-1031.32
  https://launchpad.net/ubuntu/+source/linux-oracle/5.4.0-1034.36
  https://launchpad.net/ubuntu/+source/linux-raspi/5.4.0-1026.29
  https://launchpad.net/ubuntu/+source/linux-aws-5.4/5.4.0-1034.35~18.04.1
  https://launchpad.net/ubuntu/+source/linux-azure-5.4/5.4.0-1035.36~18.04.1
  https://launchpad.net/ubuntu/+source/linux-gcp-5.4/5.4.0-1033.35~18.04.1
  https://launchpad.net/ubuntu/+source/linux-gke-5.4/5.4.0-1033.35~18.04.1
  https://launchpad.net/ubuntu/+source/linux-hwe-5.4/5.4.0-59.65~18.04.1
  https://launchpad.net/ubuntu/+source/linux-oracle-5.4/5.4.0-1034.36~18.04.1
  https://launchpad.net/ubuntu/+source/linux-raspi-5.4/5.4.0-1026.29~18.04.1