USN-4679-1: Linux kernel vulnerabilities

06 January 2021

Several security issues were fixed in the Linux kernel.

Releases

Packages

  • linux - Linux kernel
  • linux-aws - Linux kernel for Amazon Web Services (AWS) systems
  • linux-aws-5.4 - Linux kernel for Amazon Web Services (AWS) systems
  • linux-azure - Linux kernel for Microsoft Azure Cloud systems
  • linux-azure-5.4 - Linux kernel for Microsoft Azure cloud systems
  • linux-gcp - Linux kernel for Google Cloud Platform (GCP) 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-kvm - Linux kernel for cloud environments
  • linux-oracle - Linux kernel for Oracle Cloud systems
  • linux-oracle-5.4 - Linux kernel for Oracle Cloud systems
  • linux-raspi - Linux kernel for Raspberry Pi (V8) 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
Ubuntu 18.04

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.

Related notices

  • USN-4681-1: linux-image-powerpc-smp-lts-xenial, linux-aws, linux-image-generic-lpae-lts-xenial, linux-image-4.4.0-198-powerpc64-smp, linux-image-kvm, linux-image-powerpc-e500mc-lts-xenial, linux-image-powerpc64-smp, linux-image-snapdragon, linux-image-generic-lts-xenial, linux, linux-image-4.4.0-198-lowlatency, linux-image-powerpc64-smp-lts-xenial, linux-image-4.4.0-198-powerpc-smp, linux-image-virtual-lts-xenial, linux-image-4.4.0-1147-snapdragon, linux-raspi2, linux-image-4.4.0-198-generic, linux-kvm, linux-image-4.4.0-198-powerpc64-emb, linux-image-virtual, linux-image-lowlatency, linux-image-4.4.0-1143-raspi2, linux-image-4.4.0-198-generic-lpae, linux-image-powerpc64-emb, linux-image-powerpc-e500mc, linux-image-aws, linux-snapdragon, linux-image-raspi2, linux-image-lowlatency-lts-xenial, linux-image-4.4.0-1083-aws, linux-image-generic-lpae, linux-image-4.4.0-1119-aws, linux-image-4.4.0-198-powerpc-e500mc, linux-image-powerpc64-emb-lts-xenial, linux-image-generic, linux-image-4.4.0-1085-kvm, linux-lts-xenial, linux-image-powerpc-smp
  • USN-4680-1: linux-image-oracle, linux-hwe, linux-gcp, linux-image-4.15.0-129-lowlatency, linux-image-4.15.0-129-generic, linux-aws, linux-azure-4.15, linux-image-4.15.0-1091-aws, linux-image-gke-4.15, linux-image-kvm, linux-image-lowlatency-hwe-16.04, linux-gke-4.15, linux-image-generic-lpae-hwe-16.04, linux-image-gcp-lts-18.04, linux, linux-image-powerpc64-smp, linux-image-snapdragon, linux-image-aws-lts-18.04, linux-raspi2, linux-image-virtual-hwe-16.04, linux-kvm, linux-image-virtual, linux-image-lowlatency, linux-image-4.15.0-1103-azure, linux-image-gke, linux-azure, linux-gcp-4.15, linux-image-azure-lts-18.04, linux-image-powerpc64-emb, linux-image-powerpc-e500mc, linux-image-azure, linux-snapdragon, linux-image-4.15.0-1077-raspi2, linux-image-4.15.0-1077-gke, linux-image-oracle-lts-18.04, linux-image-gcp, linux-image-raspi2, linux-image-4.15.0-1094-snapdragon, linux-oracle, linux-aws-hwe, linux-image-generic-lpae, linux-image-4.15.0-1082-kvm, linux-image-4.15.0-129-generic-lpae, linux-image-aws-hwe, linux-image-generic-hwe-16.04, linux-image-generic, linux-image-oem, linux-image-4.15.0-1062-oracle, linux-image-powerpc-smp, linux-image-4.15.0-1091-gcp
  • USN-4683-1: linux-image-5.6.0-1039-oem, linux-oem-5.6, linux-image-oem-20.04