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Kernel Live Patch Security Notice LSN-0081-1

Kernel Live Patch Security Notice LSN-0081-1
Posted Sep 14, 2021
Authored by Benjamin M. Romer

Maxim Levitsky discovered that the KVM hypervisor implementation for AMD processors in the Linux kernel did not properly prevent a guest VM from enabling AVIC in nested guest VMs. An attacker in a guest VM could use this to write to portions of the host’s physical memory. Maxim Levitsky and Paolo Bonzini discovered that the KVM hypervisor implementation for AMD processors in the Linux kernel allowed a guest VM to disable restrictions on VMLOAD/VMSAVE in a nested guest. An attacker in a guest VM could use this to read or write portions of the host's physical memory. Various other vulnerabilities were also addressed.

tags | advisory, kernel, vulnerability
systems | linux
advisories | CVE-2021-22555, CVE-2021-33909, CVE-2021-3653, CVE-2021-3656
MD5 | 466908f10276ab3196dea532b09d7715

Kernel Live Patch Security Notice LSN-0081-1

Change Mirror Download
Linux kernel vulnerabilities

A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 ESM
- Ubuntu 14.04 ESM

Summary

Several security issues were fixed in the kernel.

Software Description

- linux - Linux kernel
- linux-gcp - Linux kernel for Google Cloud Platform (GCP) systems
- linux-gke - Linux kernel for Google Container Engine (GKE) systems
- linux-gkeop - Linux kernel for Google Container Engine (GKE) systems
- linux-oem - Linux kernel for OEM systems

Details

Maxim Levitsky discovered that the KVM hypervisor implementation for AMD
processors in the Linux kernel did not properly prevent a guest VM from
enabling AVIC in nested guest VMs. An attacker in a guest VM could use
this to write to portions of the host’s physical memory. (CVE-2021-3653)

Maxim Levitsky and Paolo Bonzini discovered that the KVM hypervisor
implementation for AMD processors in the Linux kernel allowed a guest VM
to disable restrictions on VMLOAD/VMSAVE in a nested guest. An attacker
in a guest VM could use this to read or write portions of the host’s
physical memory. (CVE-2021-3656)

Andy Nguyen discovered that the netfilter subsystem in the Linux kernel
contained an out-of-bounds write in its setsockopt() implementation. A
local attacker could use this to cause a denial of service (system
crash) or possibly execute arbitrary code. (CVE-2021-22555)

It was discovered that the virtual file system implementation in the
Linux kernel contained an unsigned to signed integer conversion error. A
local attacker could use this to cause a denial of service (system
crash) or execute arbitrary code. (CVE-2021-33909)

Update instructions

The problem can be corrected by updating your kernel livepatch to the
following versions:

Ubuntu 20.04 LTS
gcp - 81.1
generic - 81.1
gke - 81.1
gkeop - 81.1
lowlatency - 81.1

Ubuntu 18.04 LTS
generic - 81.1
gke - 81.1
gkeop - 81.1
lowlatency - 81.1
oem - 81.1

Ubuntu 16.04 ESM
generic - 81.1
lowlatency - 81.1

Ubuntu 14.04 ESM
generic - 81.1
lowlatency - 81.1

Support Information

Kernels older than the levels listed below do not receive livepatch
updates. If you are running a kernel version earlier than the one listed
below, please upgrade your kernel as soon as possible.

Ubuntu 20.04 LTS
linux-aws - 5.4.0-1009
linux-azure - 5.4.0-1010
linux-gcp - 5.4.0-1009
linux-gke - 5.4.0-1033
linux-gkeop - 5.4.0-1009
linux-oem - 5.4.0-26
linux - 5.4.0-26

Ubuntu 18.04 LTS
linux-aws - 4.15.0-1054
linux-gke-4.15 - 4.15.0-1076
linux-gke-5.4 - 5.4.0-1009
linux-gkeop-5.4 - 5.4.0-1007
linux-hwe-5.4 - 5.4.0-26
linux-oem - 4.15.0-1063
linux - 4.15.0-69

Ubuntu 16.04 ESM
linux-aws - 4.4.0-1098
linux-azure - 4.15.0-1063
linux-azure - 4.15.0-1078
linux-hwe - 4.15.0-69
linux - 4.4.0-168
linux - 4.4.0-211

Ubuntu 14.04 ESM
linux-lts-xenial - 4.4.0-168

References

- CVE-2021-3653
- CVE-2021-3656
- CVE-2021-22555
- CVE-2021-33909



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