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-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

Jann Horn discovered that the tty subsystem of the Linux kernel did not
use consistent locking in some situations, leading to a read-after-free
vulnerability. A local attacker could use this to cause a denial of
service (system crash) or possibly expose sensitive information (kernel
memory). (CVE-2020-29660)

Jann Horn discovered a race condition in the tty subsystem of the Linux
kernel in the locking for the TIOCSPGRP ioctl(), leading to a use-after-
free vulnerability. A local attacker could use this to cause a denial of
service (system crash) or possibly execute arbitrary code.
(CVE-2020-29661)

De4dCr0w of 360 Alpha Lab discovered that the BPF verifier in the Linux
kernel did not properly handle mod32 destination register truncation
when the source register was known to be 0. A local attacker could use
this to expose sensitive information (kernel memory) or possibly execute
arbitrary code. (CVE-2021-3444)

kernel: use-after-free in route4_change() in net/sched/cls_route.c 
(CVE-2021-3715)

Update instructions

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

Ubuntu 20.04 LTS
    gcp - 82.2
    generic - 82.2
    gke - 82.2
    gkeop - 82.2
    lowlatency - 82.2

Ubuntu 18.04 LTS
    generic - 82.1
    generic - 82.2
    gke - 82.1
    gke - 82.2
    gkeop - 82.2
    lowlatency - 82.1
    lowlatency - 82.2
    oem - 82.1
    oem - 82.2

Ubuntu 16.04 ESM
    generic - 82.1
    generic - 82.2
    lowlatency - 82.1
    lowlatency - 82.2

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 - 4.15.0-69
    linux - 4.4.0-168

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

References

-   CVE-2020-29660
-   CVE-2020-29661
-   CVE-2021-3444
-   CVE-2021-3715



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