==========================================================================
Ubuntu Security Notice USN-4751-1
February 25, 2021

linux, linux-aws, linux-azure, linux-gcp, linux-hwe-5.8, linux-kvm,
linux-oracle, linux-raspi vulnerabilities
==========================================================================

A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 20.10
- Ubuntu 20.04 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-hwe-5.8: Linux hardware enablement (HWE) kernel

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 (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:

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

Ubuntu 20.10:
  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

Ubuntu 20.04 LTS:
  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

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/4751-1
  CVE-2020-25656, CVE-2020-25668, CVE-2020-25669, CVE-2020-25704,
  CVE-2020-27673, CVE-2020-27675, CVE-2020-27777, CVE-2020-27815,
  CVE-2020-27830, CVE-2020-27835, CVE-2020-28588, CVE-2020-28941,
  CVE-2020-28974, CVE-2020-29568, CVE-2020-29569, CVE-2020-29660,
  CVE-2020-29661, CVE-2020-35508

Package Information:
  https://launchpad.net/ubuntu/+source/linux/5.8.0-44.50
  https://launchpad.net/ubuntu/+source/linux-aws/5.8.0-1024.26
  https://launchpad.net/ubuntu/+source/linux-azure/5.8.0-1023.25
  https://launchpad.net/ubuntu/+source/linux-gcp/5.8.0-1023.24
  https://launchpad.net/ubuntu/+source/linux-kvm/5.8.0-1019.21
  https://launchpad.net/ubuntu/+source/linux-oracle/5.8.0-1021.22
  https://launchpad.net/ubuntu/+source/linux-raspi/5.8.0-1016.19
  https://launchpad.net/ubuntu/+source/linux-hwe-5.8/5.8.0-44.50~20.04.1