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

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

The BPF subsystem in the Linux kernel before 4.17
mishandles situations with a long jump over an instruction sequence
where inner instructions require substantial expansions into multiple
BPF instructions, leading to an overflow. This affects kernel/bpf/core.c
and net/core/filter.c. (CVE-2018-25020)

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)

Nadav Amit discovered that the hugetlb implementation in the Linux
kernel did not perform TLB flushes under certain conditions. A local
attacker could use this to leak or alter data from other processes that
use huge pages. (CVE-2021-4002)

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
    aws - 83.1
    azure - 83.1
    gcp - 83.1
    generic - 83.1
    gke - 83.1
    gkeop - 83.1
    lowlatency - 83.1

Ubuntu 18.04 LTS
    aws - 83.1
    generic - 83.1
    gke - 83.1
    gke - 83.2
    gkeop - 83.1
    gkeop - 83.2
    lowlatency - 83.1
    oem - 83.1

Ubuntu 16.04 ESM
    aws - 83.1
    azure - 83.1
    generic - 83.1
    lowlatency - 83.1

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-azure-4.15 - 4.15.0-1115
    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-hwe - 4.15.0-143
    linux - 4.4.0-168

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

References

-   CVE-2018-25020
-   CVE-2021-3653
-   CVE-2021-4002
-   CVE-2021-22555
-   CVE-2021-33909



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