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USN-4679-1: Linux kernel vulnerabilities

6 January 2021

Several security issues were fixed in the Linux kernel.

Releases

Packages

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-4680-1: linux-image-oracle-lts-18.04, linux-image-4.15.0-1077-gke, linux-image-4.15.0-129-generic-lpae, linux-image-4.15.0-1077-raspi2, linux-image-lowlatency, linux-aws, linux-image-gke-4.15, linux-hwe, linux-gcp, linux-image-gcp-lts-18.04, linux-gke-4.15, linux-image-azure-lts-18.04, linux-image-virtual-hwe-16.04-edge, linux-gcp-4.15, linux-azure-4.15, linux-raspi2, linux-image-lowlatency-hwe-16.04, linux-image-4.15.0-1103-azure, linux-azure, linux-aws-hwe, linux-image-4.15.0-129-lowlatency, linux-image-generic-lpae-hwe-16.04-edge, linux, linux-image-aws-hwe, linux-image-oem, linux-image-snapdragon, linux-image-raspi2, linux-snapdragon, linux-image-generic-hwe-16.04-edge, linux-image-4.15.0-1091-aws, linux-oracle, linux-image-lowlatency-hwe-16.04-edge, linux-image-4.15.0-1091-gcp, linux-image-4.15.0-1062-oracle, linux-image-4.15.0-1082-kvm, linux-image-virtual-hwe-16.04, linux-image-generic, linux-image-generic-lpae, linux-image-gcp, linux-image-generic-lpae-hwe-16.04, linux-image-4.15.0-1094-snapdragon, linux-image-4.15.0-129-generic, linux-image-virtual, linux-image-aws-lts-18.04, linux-image-generic-hwe-16.04, linux-image-azure, linux-image-gke, linux-image-azure-edge, linux-image-oracle, linux-kvm, linux-image-kvm
  • USN-4681-1: linux-image-powerpc-smp-lts-utopic, linux-image-powerpc64-smp-lts-wily, linux-image-powerpc64-smp-lts-vivid, linux-image-lowlatency-lts-xenial, linux-image-generic-lpae-lts-utopic, linux-image-lowlatency, linux-lts-xenial, linux-aws, linux-image-virtual-lts-vivid, linux-image-powerpc64-smp-lts-xenial, linux-image-powerpc-smp-lts-xenial, linux-image-virtual-lts-wily, linux-image-powerpc64-emb-lts-xenial, linux-image-virtual-lts-xenial, linux-image-generic-lpae-lts-vivid, linux-image-powerpc64-smp-lts-utopic, linux-raspi2, linux-image-4.4.0-1085-kvm, linux-image-4.4.0-1143-raspi2, linux-image-lowlatency-lts-wily, linux-image-4.4.0-198-generic-lpae, linux, linux-image-generic-lts-vivid, linux-image-generic-lts-xenial, linux-image-generic-lts-wily, linux-image-4.4.0-198-powerpc-e500mc, linux-image-raspi2, linux-image-snapdragon, linux-image-4.4.0-198-generic, linux-snapdragon, linux-image-powerpc64-emb-lts-utopic, linux-image-4.4.0-198-powerpc64-emb, linux-image-lowlatency-lts-utopic, linux-image-powerpc64-emb-lts-vivid, linux-image-aws, linux-image-4.4.0-1083-aws, linux-image-generic-lts-utopic, linux-image-4.4.0-1119-aws, linux-image-generic-lpae-lts-xenial, linux-image-powerpc64-emb, linux-image-powerpc-smp, linux-image-powerpc-smp-lts-wily, linux-image-powerpc64-smp, linux-image-virtual-lts-utopic, linux-image-powerpc-e500mc-lts-utopic, linux-image-generic, linux-image-generic-lpae, linux-image-powerpc-smp-lts-vivid, linux-image-lowlatency-lts-vivid, linux-image-powerpc-e500mc, linux-image-powerpc-e500mc-lts-vivid, linux-image-4.4.0-1147-snapdragon, linux-image-4.4.0-198-powerpc-smp, linux-image-4.4.0-198-powerpc64-smp, linux-image-powerpc64-emb-lts-wily, linux-image-virtual, linux-image-4.4.0-198-lowlatency, linux-image-generic-lpae-lts-wily, linux-image-powerpc-e500mc-lts-wily, linux-kvm, linux-image-kvm, linux-image-powerpc-e500mc-lts-xenial
  • USN-4683-1: linux-image-5.6.0-1039-oem, linux-oem-5.6, linux-image-oem-20.04
  • USN-4751-1: linux-image-generic-64k-hwe-20.04, linux-image-5.8.0-1016-raspi, linux-image-virtual-hwe-20.04, linux-image-lowlatency, linux-aws, linux-image-5.8.0-1024-aws, linux-image-5.8.0-44-generic-lpae, linux-gcp, linux-image-5.8.0-1021-oracle, linux-image-5.8.0-44-generic, linux-image-5.8.0-1016-raspi-nolpae, linux-image-lowlatency-hwe-20.04-edge, linux-image-5.8.0-1019-kvm, linux-image-lowlatency-hwe-20.04, linux-azure, linux, linux-image-virtual-hwe-20.04-edge, linux-raspi, linux-image-5.8.0-44-generic-64k, linux-image-generic-lpae-hwe-20.04-edge, linux-oracle, linux-image-generic-hwe-20.04-edge, linux-image-aws, linux-image-raspi-nolpae, linux-image-5.8.0-1023-gcp, linux-image-oem-20.04, linux-image-5.8.0-44-lowlatency, linux-image-generic, linux-image-generic-lpae, linux-image-gcp, linux-image-generic-lpae-hwe-20.04, linux-image-virtual, linux-image-generic-64k, linux-image-azure, linux-image-gke, linux-image-oracle, linux-kvm, linux-image-kvm, linux-image-generic-64k-hwe-20.04-edge, linux-image-5.8.0-1023-azure, linux-image-raspi, linux-hwe-5.8, linux-image-generic-hwe-20.04
  • USN-4710-1: linux-image-4.15.0-135-lowlatency, linux-image-4.15.0-133-lowlatency, linux-image-lowlatency, linux-image-4.15.0-133-generic-lpae, linux-hwe, linux-image-virtual-hwe-16.04-edge, linux-image-4.15.0-135-generic, linux-image-lowlatency-hwe-16.04, linux-image-generic-lpae-hwe-16.04-edge, linux, linux-image-oem, linux-image-generic-hwe-16.04-edge, linux-image-lowlatency-hwe-16.04-edge, linux-image-4.15.0-135-generic-lpae, linux-image-4.15.0-133-generic, linux-image-virtual-hwe-16.04, linux-image-generic, linux-image-generic-lpae, linux-image-generic-lpae-hwe-16.04, linux-image-virtual, linux-image-generic-hwe-16.04
  • USN-4711-1: linux-image-oracle-lts-18.04, linux-image-4.15.0-1095-snapdragon, linux-aws, linux-image-gke-4.15, linux-gcp, linux-image-gcp-lts-18.04, linux-gke-4.15, linux-image-4.15.0-1078-gke, linux-image-azure-lts-18.04, linux-gcp-4.15, linux-azure-4.15, linux-raspi2, linux-image-4.15.0-1092-gcp, linux-image-4.15.0-1106-azure, linux-azure, linux-aws-hwe, linux-image-aws-hwe, linux-image-snapdragon, linux-image-raspi2, linux-snapdragon, linux-image-4.15.0-1093-aws, linux-oracle, linux-image-4.15.0-1064-oracle, linux-image-4.15.0-1078-raspi2, linux-image-gcp, linux-image-aws-lts-18.04, linux-image-azure, linux-image-gke, linux-image-azure-edge, linux-image-oracle, linux-kvm, linux-image-kvm, linux-image-4.15.0-1084-kvm
  • USN-4752-1: linux-image-5.6.0-1048-oem, linux-oem-5.6, linux-image-oem-20.04
  • USN-4708-1: linux-image-4.4.0-201-powerpc-smp, linux-image-powerpc-smp-lts-utopic, linux-image-powerpc64-smp-lts-wily, linux-image-powerpc64-smp-lts-vivid, linux-image-lowlatency-lts-xenial, linux-image-generic-lpae-lts-utopic, linux-image-4.4.0-201-generic, linux-image-lowlatency, linux-lts-xenial, linux-image-virtual-lts-vivid, linux-image-virtual-lts-wily, linux-image-powerpc64-smp-lts-xenial, linux-image-powerpc-smp-lts-xenial, linux-image-4.4.0-201-powerpc64-emb, linux-image-powerpc64-emb-lts-xenial, linux-image-virtual-lts-xenial, linux-image-generic-lpae-lts-vivid, linux-image-powerpc64-smp-lts-utopic, linux-image-lowlatency-lts-wily, linux-image-generic-lts-vivid, linux, linux-image-generic-lts-xenial, linux-image-generic-lts-wily, linux-image-4.4.0-201-generic-lpae, linux-image-4.4.0-201-lowlatency, linux-image-powerpc64-emb-lts-utopic, linux-image-lowlatency-lts-utopic, linux-image-powerpc64-emb-lts-vivid, linux-image-generic-lts-utopic, linux-image-4.4.0-201-powerpc64-smp, linux-image-generic-lpae-lts-xenial, linux-image-powerpc64-emb, linux-image-powerpc-smp, linux-image-powerpc-smp-lts-wily, linux-image-powerpc64-smp, linux-image-virtual-lts-utopic, linux-image-4.4.0-201-powerpc-e500mc, linux-image-powerpc-e500mc-lts-utopic, linux-image-generic, linux-image-generic-lpae, linux-image-powerpc-smp-lts-vivid, linux-image-lowlatency-lts-vivid, linux-image-powerpc-e500mc, linux-image-powerpc-e500mc-lts-vivid, linux-image-powerpc64-emb-lts-wily, linux-image-virtual, linux-image-generic-lpae-lts-wily, linux-image-powerpc-e500mc-lts-wily, linux-image-powerpc-e500mc-lts-xenial