[LSN-0076-1] 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 LTS
-   Ubuntu 14.04 ESM

Summary

Several security issues were fixed in the kernel.

Software Description

-   linux - Linux kernel
-   linux-aws - Linux kernel for Amazon Web Services (AWS) systems
-   linux-azure - Linux kernel for Microsoft Azure Cloud systems
-   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

It was discovered that the overlayfs implementation in the Linux kernel
did not properly validate the application of file system capabilities
with respect to user namespaces. A local attacker could use this to
gain
elevated privileges. (CVE-2021-3493)

Piotr Krysiuk discovered that the BPF JIT compiler for x86 in the Linux
kernel did not properly validate computation of branch displacements in
some situations. A local attacker could use this to cause a denial of
service (system crash) or possibly execute arbitrary code.
(CVE-2021-29154)

Update instructions

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

Ubuntu 20.04 LTS
    aws - 76.3
    azure - 76.3
    gcp - 76.3
    generic - 76.3
    gke - 76.3
    gkeop - 76.3
    lowlatency - 76.3

Ubuntu 18.04 LTS
    aws - 76.2
    generic - 76.3
    gke - 76.3
    gkeop - 76.3
    lowlatency - 76.3
    oem - 76.2

Ubuntu 16.04 LTS
    aws - 76.1
    azure - 76.2
    generic - 76.2
    lowlatency - 76.2

Ubuntu 14.04 ESM
    generic - 76.1
    lowlatency - 76.1

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 LTS
    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

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

References

-   CVE-2021-3493
-   CVE-2021-29154