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Ubuntu 20.04 LTS: USN-5091-3 Critical Kernel Azure Regression: DoS Issue

ubuntu
Calendar Grey October 14, 2021
Dist Ubuntu Esm H88
Tackling performance challenges in the Linux kernel for AWS. Enhance your system resilience now!
USN-5091-1 introduced a regression in the Linux kernel for Microsoft Azure cloud systems.

Summary

USN-5091-1 introduced a regression in the Linux kernel for Microsoft

Azure cloud systems.

Software Description:

- linux-azure: Linux kernel for Microsoft Azure Cloud systems

- linux-azure-5.4: Linux kernel for Microsoft Azure cloud systems

Details:

USN-5091-1 fixed vulnerabilities in Linux 5.4-based kernels.

Unfortunately, for Linux kernels intended for use within Microsoft

Azure environments, that update introduced a regression that could

cause the kernel to fail to boot in large Azure instance types.

This update fixes the problem.

We apologize for the inconvenience.

Original advisory 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 tra...

Read the Full Advisory

Topics%20covered

Topics Covered

security advisory update doS ubuntu kernel regression azure

Update Instructions

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

Ubuntu 20.04 LTS:
  linux-image-5.4.0-1061-azure    5.4.0-1061.64
  linux-image-azure-lts-20.04     5.4.0.1061.59

Ubuntu 18.04 LTS:
  linux-image-5.4.0-1061-azure    5.4.0-1061.64~18.04.1
  linux-image-azure               5.4.0.1061.41

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-5091-3

https://ubuntu.com/security/notices/USN-5091-1

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1940564

Severity
critical
Lowest
Low
Medium
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Critical

October 15, 2021

Topics%20covered

Topics Covered

security advisory update doS ubuntu kernel regression azure

Package Information

https://launchpad.net/ubuntu/+source/linux-azure/5.4.0-1061.64
https://launchpad.net/ubuntu/+source/linux-azure-5.4/5.4.0-1061.64~18.04.1

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