=========================================================================Ubuntu Security Notice USN-5644-1
September 27, 2022

linux-gcp-5.15 vulnerabilities
=========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 20.04 LTS

Summary:

Several security issues were fixed in the Linux kernel.

Software Description:
- linux-gcp-5.15: Linux kernel for Google Cloud Platform (GCP) systems

Details:

It was discovered that the framebuffer driver on the Linux kernel did not
verify size limits when changing font or screen size, leading to an out-of-bounds write. A local attacker could use this to cause a denial of service
(system crash) or possibly execute arbitrary code. (CVE-2021-33655)

Duoming Zhou discovered that race conditions existed in the timer handling
implementation of the Linux kernel's Rose X.25 protocol layer, resulting in
use-after-free vulnerabilities. A local attacker could use this to cause a
denial of service (system crash). (CVE-2022-2318)

Roger Pau Monné discovered that the Xen virtual block driver in the Linux
kernel did not properly initialize memory pages to be used for shared
communication with the backend. A local attacker could use this to expose
sensitive information (guest kernel memory). (CVE-2022-26365)

Roger Pau Monné discovered that the Xen paravirtualization frontend in the
Linux kernel did not properly initialize memory pages to be used for shared
communication with the backend. A local attacker could use this to expose
sensitive information (guest kernel memory). (CVE-2022-33740)

It was discovered that the Xen paravirtualization frontend in the Linux
kernel incorrectly shared unrelated data when communicating with certain
backends. A local attacker could use this to cause a denial of service
(guest crash) or expose sensitive information (guest kernel memory).
(CVE-2022-33741, CVE-2022-33742)

Jan Beulich discovered that the Xen network device frontend driver in the
Linux kernel incorrectly handled socket buffers (skb) references when
communicating with certain backends. A local attacker could use this to
cause a denial of service (guest crash). (CVE-2022-33743)

Oleksandr Tyshchenko discovered that the Xen paravirtualization platform in
the Linux kernel on ARM platforms contained a race condition in certain
situations. An attacker in a guest VM could use this to cause a denial of
service in the host OS. (CVE-2022-33744)

It was discovered that the virtio RPMSG bus driver in the Linux kernel
contained a double-free vulnerability in certain error conditions. A local
attacker could possibly use this to cause a denial of service (system
crash). (CVE-2022-34494, CVE-2022-34495)

Domingo Dirutigliano and Nicola Guerrera discovered that the netfilter
subsystem in the Linux kernel did not properly handle rules that truncated
packets below the packet header size. When such rules are in place, a
remote attacker could possibly use this to cause a denial of service
(system crash). (CVE-2022-36946)

Update instructions:

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

Ubuntu 20.04 LTS:
   linux-image-5.15.0-1018-gcp     5.15.0-1018.24~20.04.1
   linux-image-gcp                 5.15.0.1018.24~20.04.1

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-5644-1
   CVE-2021-33655, CVE-2022-2318, CVE-2022-26365, CVE-2022-33740,
   CVE-2022-33741, CVE-2022-33742, CVE-2022-33743, CVE-2022-33744,
   CVE-2022-34494, CVE-2022-34495, CVE-2022-36946

Package Information:
   https://launchpad.net/ubuntu/+source/linux-gcp-5.15/5.15.0-1018.24~20.04.1