A Linux kernel (Raspberry Pi) security update has been released for Ubuntu 18.04 LTS and 20.04 LTS.

USN-5091-2: Linux kernel (Raspberry Pi) vulnerabilities

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Ubuntu Security Notice USN-5091-2
September 30, 2021

linux-raspi, linux-raspi-5.4 vulnerabilities
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS

Summary:

Several security issues were fixed in the Linux kernel.

Software Description:
- linux-raspi: Linux kernel for Raspberry Pi systems
- linux-raspi-5.4: Linux kernel for Raspberry Pi systems

Details:

Ofek Kirzner, Adam Morrison, Benedict Schlueter, and Piotr Krysiuk
discovered that the BPF verifier in the Linux kernel missed possible
mispredicted branches due to type confusion, allowing a side-channel
attack. An attacker could use this to expose sensitive information.
(CVE-2021-33624)

It was discovered that the tracing subsystem in the Linux kernel did not
properly keep track of per-cpu ring buffer state. A privileged attacker
could use this to cause a denial of service. (CVE-2021-3679)

It was discovered that the Virtio console implementation in the Linux
kernel did not properly validate input lengths in some situations. A local
attacker could possibly use this to cause a denial of service (system
crash). (CVE-2021-38160)

Michael Wakabayashi discovered that the NFSv4 client implementation in the
Linux kernel did not properly order connection setup operations. An
attacker controlling a remote NFS server could use this to cause a denial
of service on the client. (CVE-2021-38199)

It was discovered that the MAX-3421 host USB device driver in the Linux
kernel did not properly handle device removal events. A physically
proximate attacker could use this to cause a denial of service (system
crash). (CVE-2021-38204)

Update instructions:

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

Ubuntu 20.04 LTS:
linux-image-5.4.0-1044-raspi 5.4.0-1044.48
linux-image-raspi 5.4.0.1044.79
linux-image-raspi2 5.4.0.1044.79

Ubuntu 18.04 LTS:
linux-image-5.4.0-1044-raspi 5.4.0-1044.48~18.04.1
linux-image-raspi-hwe-18.04 5.4.0.1044.47

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://ubuntu.com/security/notices/USN-5091-2
  https://ubuntu.com/security/notices/USN-5091-1
CVE-2021-33624, CVE-2021-3679, CVE-2021-38160, CVE-2021-38199,
CVE-2021-38204

Package Information:
  https://launchpad.net/ubuntu/+source/linux-raspi/5.4.0-1044.48
  https://launchpad.net/ubuntu/+source/linux-raspi-5.4/5.4.0-1044.48~18.04.1