[LSN-0081-1] Linux kernel vulnerability

[benjamin.romer at canonical.com]

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