1. Ubuntu Security Notices
  2. USN-4751-1

USN-4751-1: Linux kernel vulnerabilities

Publication date

25 February 2021

Overview

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-azure - Linux kernel for Microsoft Azure Cloud systems
  • linux-gcp - Linux kernel for Google Cloud Platform (GCP) systems
  • linux-hwe-5.8 - Linux hardware enablement (HWE) kernel
  • linux-kvm - Linux kernel for cloud environments
  • linux-oracle - Linux kernel for Oracle Cloud systems
  • linux-raspi - 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)

Bodong Zhao discovered a use-after-free in the Sun keyboard driver
implementation in the Linux kernel. A local attacker could use this to
cause a denial of service or possibly execute arbitrary code.
(CVE-2020-25669)

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...

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)

Bodong Zhao discovered a use-after-free in the Sun keyboard driver
implementation in the Linux kernel. A local attacker could use this to
cause a denial of service or possibly execute arbitrary code.
(CVE-2020-25669)

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)

Julien Grall discovered that the Xen dom0 event handler in the Linux kernel
did not properly limit the number of events queued. An attacker in a guest
VM could use this to cause a denial of service in the host OS.
(CVE-2020-27673)

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)

It was discovered that the jfs file system implementation in the Linux
kernel contained an out-of-bounds read vulnerability. A local attacker
could use this to possibly cause a denial of service (system crash).
(CVE-2020-27815)

Shisong Qin and Bodong Zhao discovered that Speakup screen reader driver in
the Linux kernel did not correctly handle setting line discipline in some
situations. A local attacker could use this to cause a denial of service
(system crash). (CVE-2020-27830, CVE-2020-28941)

It was discovered that a use-after-free vulnerability existed in the
infiniband hfi1 device driver in the Linux kernel. A local attacker could
possibly use this to cause a denial of service (system crash).
(CVE-2020-27835)

It was discovered that an information leak existed in the syscall
implementation in the Linux kernel on 32 bit systems. A local attacker
could use this to expose sensitive information (kernel memory).
(CVE-2020-28588)

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)

Michael Kurth and Pawel Wieczorkiewicz discovered that the Xen event
processing backend in the Linux kernel did not properly limit the number of
events queued. An attacker in a guest VM could use this to cause a denial
of service in the host OS. (CVE-2020-29568)

Olivier Benjamin and Pawel Wieczorkiewicz discovered a race condition the
Xen paravirt block backend in the Linux kernel, leading to a use-after-free
vulnerability. An attacker in a guest VM could use this to cause a denial
of service in the host OS. (CVE-2020-29569)

Jann Horn discovered that the tty subsystem of the Linux kernel did not use
consistent locking in some situations, leading to a read-after-free
vulnerability. A local attacker could use this to cause a denial of service
(system crash) or possibly expose sensitive information (kernel memory).
(CVE-2020-29660)

Jann Horn discovered a race condition in the tty subsystem of the Linux
kernel in the locking for the TIOCSPGRP ioctl(), leading to a use-after-
free vulnerability. A local attacker could use this to cause a denial of
service (system crash) or possibly execute arbitrary code. (CVE-2020-29661)

It was discovered that a race condition existed that caused the Linux
kernel to not properly restrict exit signal delivery. A local attacker
could possibly use this to send signals to arbitrary processes.
(CVE-2020-35508)

Update instructions

After a standard system update you need to reboot your computer to make all the necessary changes.

Learn more about how to get the fixes.

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.

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

Ubuntu Release Package Version
20.10 groovy linux-image-5.8.0-1016-raspi –  5.8.0-1016.19
linux-image-5.8.0-1016-raspi-nolpae –  5.8.0-1016.19
linux-image-5.8.0-1019-kvm –  5.8.0-1019.21
linux-image-5.8.0-1021-oracle –  5.8.0-1021.22
linux-image-5.8.0-1023-azure –  5.8.0-1023.25
linux-image-5.8.0-1023-gcp –  5.8.0-1023.24
linux-image-5.8.0-1024-aws –  5.8.0-1024.26
linux-image-5.8.0-44-generic –  5.8.0-44.50
linux-image-5.8.0-44-generic-64k –  5.8.0-44.50
linux-image-5.8.0-44-generic-lpae –  5.8.0-44.50
linux-image-5.8.0-44-lowlatency –  5.8.0-44.50
linux-image-aws –  5.8.0.1024.26
linux-image-azure –  5.8.0.1023.23
linux-image-gcp –  5.8.0.1023.23
linux-image-generic –  5.8.0.44.49
linux-image-generic-64k –  5.8.0.44.49
linux-image-generic-lpae –  5.8.0.44.49
linux-image-gke –  5.8.0.1023.23
linux-image-kvm –  5.8.0.1019.21
linux-image-lowlatency –  5.8.0.44.49
linux-image-oem-20.04 –  5.8.0.44.49
linux-image-oracle –  5.8.0.1021.20
linux-image-raspi –  5.8.0.1016.19
linux-image-raspi-nolpae –  5.8.0.1016.19
linux-image-virtual –  5.8.0.44.49
20.04 focal linux-image-5.8.0-44-generic –  5.8.0-44.50~20.04.1
linux-image-5.8.0-44-generic-lpae –  5.8.0-44.50~20.04.1
linux-image-5.8.0-44-lowlatency –  5.8.0-44.50~20.04.1
linux-image-generic-64k-hwe-20.04 –  5.8.0.44.50~20.04.30
linux-image-generic-hwe-20.04 –  5.8.0.44.50~20.04.30
linux-image-generic-lpae-hwe-20.04 –  5.8.0.44.50~20.04.30
linux-image-lowlatency-hwe-20.04 –  5.8.0.44.50~20.04.30
linux-image-virtual-hwe-20.04 –  5.8.0.44.50~20.04.30

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References

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