USN-4679-1: Linux kernel vulnerabilities

Publication date

6 January 2021

Overview

Several security issues were fixed in the Linux kernel.


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...

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

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
20.04 focal 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
18.04 bionic 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

Reduce your security exposure

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