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

USN-5094-2: Linux kernel (Raspberry Pi) vulnerabilities

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Ubuntu Security Notice USN-5094-2
September 30, 2021

linux-raspi2 vulnerabilities
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 18.04 LTS

Summary:

Several security issues were fixed in the Linux kernel.

Software Description:
- linux-raspi2: Linux kernel for Raspberry Pi systems

Details:

It was discovered that the KVM hypervisor implementation in the Linux
kernel did not properly perform reference counting in some situations,
leading to a use-after-free vulnerability. An attacker who could start and
control a VM could possibly use this to expose sensitive information or
execute arbitrary code. (CVE-2021-22543)

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)

Alois Wohlschlager discovered that the overlay file system in the Linux
kernel did not restrict private clones in some situations. An attacker
could use this to expose sensitive information. (CVE-2021-3732)

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)

It was discovered that the Xilinx 10/100 Ethernet Lite device driver in the
Linux kernel could report pointer addresses in some situations. An attacker
could use this information to ease the exploitation of another
vulnerability. (CVE-2021-38205)

Update instructions:

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

Ubuntu 18.04 LTS:
linux-image-4.15.0-1096-raspi2 4.15.0-1096.102
linux-image-raspi2 4.15.0.1096.94

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-5094-2
  https://ubuntu.com/security/notices/USN-5094-1
CVE-2021-22543, CVE-2021-3679, CVE-2021-3732, CVE-2021-38204,
CVE-2021-38205

Package Information:
  https://launchpad.net/ubuntu/+source/linux-raspi2/4.15.0-1096.102