A Linux kernel regression update has been released for Ubuntu Linux 16.04 LTS and 18.04 LTS.

USN-4660-2: Linux kernel regression

=========================================================================
Ubuntu Security Notice USN-4660-2
December 13, 2020

linux, linux-aws, linux-aws-hwe, linux-azure, linux-azure-4.15, linux-gcp,
linux-gcp-4.15, linux-gke-4.15, linux-hwe, linux-kvm, linux-oracle,
linux-snapdragon regression
=========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

USN-4660-1 introduced a regression in the Linux kernel.

Software Description:
- linux: Linux kernel
- linux-aws: Linux kernel for Amazon Web Services (AWS) systems
- linux-azure-4.15: Linux kernel for Microsoft Azure Cloud systems
- linux-gcp-4.15: Linux kernel for Google Cloud Platform (GCP) systems
- linux-gke-4.15: Linux kernel for Google Container Engine (GKE) systems
- linux-kvm: Linux kernel for cloud environments
- linux-oracle: Linux kernel for Oracle Cloud systems
- linux-snapdragon: Linux kernel for Qualcomm Snapdragon processors
- linux-aws-hwe: Linux kernel for Amazon Web Services (AWS-HWE) systems
- linux-azure: Linux kernel for Microsoft Azure Cloud systems
- linux-gcp: Linux kernel for Google Cloud Platform (GCP) systems
- linux-hwe: Linux hardware enablement (HWE) kernel

Details:

USN-4660-1 fixed vulnerabilities in the Linux kernel. Unfortunately,
that update introduced a regression in the software raid10 driver
when used with fstrim that could lead to data corruption. This update
fixes the problem.

Original advisory details:

It was discovered that a race condition existed in the perf subsystem of
the Linux kernel, leading to a use-after-free vulnerability. An attacker
with access to the perf subsystem could use this to cause a denial of
service (system crash) or possibly execute arbitrary code. (CVE-2020-14351)

It was discovered that the frame buffer implementation in the Linux kernel
did not properly handle some edge cases in software scrollback. A local
attacker could use this to cause a denial of service (system crash) or
possibly execute arbitrary code. (CVE-2020-14390)

It was discovered that the netfilter connection tracker for netlink in the
Linux kernel did not properly perform bounds checking in some situations. A
local attacker could use this to cause a denial of service (system crash).
(CVE-2020-25211)

It was discovered that the Rados block device (rbd) driver in the Linux
kernel did not properly perform privilege checks for access to rbd devices
in some situations. A local attacker could use this to map or unmap rbd
block devices. (CVE-2020-25284)

It was discovered that a race condition existed in the hugetlb sysctl
implementation in the Linux kernel. A privileged attacker could use this to
cause a denial of service (system crash). (CVE-2020-25285)

It was discovered that the block layer subsystem in the Linux kernel did
not properly handle zero-length requests. A local attacker could use this
to cause a denial of service. (CVE-2020-25641)

It was discovered that the HDLC PPP implementation in the Linux kernel did
not properly validate input in some situations. A local attacker could use
this to cause a denial of service (system crash) or possibly execute
arbitrary code. (CVE-2020-25643)

It was discovered that the GENEVE tunnel implementation in the Linux kernel
when combined with IPSec did not properly select IP routes in some
situations. An attacker could use this to expose sensitive information
(unencrypted network traffic). (CVE-2020-25645)

It was discovered that the framebuffer implementation in the Linux kernel
did not properly perform range checks in certain situations. A local
attacker could use this to expose sensitive information (kernel memory).
(CVE-2020-28915)

It was discovered that Power 9 processors could be coerced to expose
information from the L1 cache in certain situations. A local attacker could
use this to expose sensitive information. (CVE-2020-4788)

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 18.04 LTS:
linux-image-4.15.0-1061-oracle 4.15.0-1061.67
linux-image-4.15.0-1076-gke 4.15.0-1076.81
linux-image-4.15.0-1081-kvm 4.15.0-1081.83
linux-image-4.15.0-1090-aws 4.15.0-1090.95
linux-image-4.15.0-1090-gcp 4.15.0-1090.103
linux-image-4.15.0-1093-snapdragon 4.15.0-1093.102
linux-image-4.15.0-1102-azure 4.15.0-1102.113
linux-image-4.15.0-128-generic 4.15.0-128.131
linux-image-4.15.0-128-generic-lpae 4.15.0-128.131
linux-image-4.15.0-128-lowlatency 4.15.0-128.131
linux-image-aws-lts-18.04 4.15.0.1090.92
linux-image-azure-lts-18.04 4.15.0.1102.75
linux-image-gcp-lts-18.04 4.15.0.1090.108
linux-image-generic 4.15.0.128.115
linux-image-generic-lpae 4.15.0.128.115
linux-image-gke 4.15.0.1076.80
linux-image-gke-4.15 4.15.0.1076.80
linux-image-kvm 4.15.0.1081.77
linux-image-lowlatency 4.15.0.128.115
linux-image-oracle-lts-18.04 4.15.0.1061.71
linux-image-powerpc-e500mc 4.15.0.128.115
linux-image-powerpc-smp 4.15.0.128.115
linux-image-powerpc64-emb 4.15.0.128.115
linux-image-powerpc64-smp 4.15.0.128.115
linux-image-snapdragon 4.15.0.1093.96
linux-image-virtual 4.15.0.128.115

Ubuntu 16.04 LTS:
linux-image-4.15.0-1061-oracle 4.15.0-1061.67~16.04.1
linux-image-4.15.0-1090-aws 4.15.0-1090.95~16.04.1
linux-image-4.15.0-1090-gcp 4.15.0-1090.103~16.04.1
linux-image-4.15.0-1102-azure 4.15.0-1102.113~16.04.1
linux-image-4.15.0-128-generic 4.15.0-128.131~16.04.1
linux-image-4.15.0-128-generic-lpae 4.15.0-128.131~16.04.1
linux-image-4.15.0-128-lowlatency 4.15.0-128.131~16.04.1
linux-image-aws-hwe 4.15.0.1090.84
linux-image-azure 4.15.0.1102.95
linux-image-gcp 4.15.0.1090.91
linux-image-generic-hwe-16.04 4.15.0.128.127
linux-image-generic-lpae-hwe-16.04 4.15.0.128.127
linux-image-gke 4.15.0.1090.91
linux-image-lowlatency-hwe-16.04 4.15.0.128.127
linux-image-oem 4.15.0.128.127
linux-image-oracle 4.15.0.1061.50
linux-image-virtual-hwe-16.04 4.15.0.128.127

After a standard system update you need to reboot your computer to make
all the necessary changes.

ATTENTION: Due to an unavoidable ABI change the kernel updates have
been given a new version number, which requires you to recompile and
reinstall all third party kernel modules you might have installed.
Unless you manually uninstalled the standard kernel metapackages
(e.g. linux-generic, linux-generic-lts-RELEASE, linux-virtual,
linux-powerpc), a standard system upgrade will automatically perform
this as well.

References:
  https://usn.ubuntu.com/4660-2
  https://usn.ubuntu.com/4660-1
  https://launchpad.net/bugs/1907262

Package Information:
  https://launchpad.net/ubuntu/+source/linux/4.15.0-128.131
  https://launchpad.net/ubuntu/+source/linux-aws/4.15.0-1090.95
  https://launchpad.net/ubuntu/+source/linux-azure-4.15/4.15.0-1102.113
  https://launchpad.net/ubuntu/+source/linux-gcp-4.15/4.15.0-1090.103
  https://launchpad.net/ubuntu/+source/linux-gke-4.15/4.15.0-1076.81
  https://launchpad.net/ubuntu/+source/linux-kvm/4.15.0-1081.83
  https://launchpad.net/ubuntu/+source/linux-oracle/4.15.0-1061.67
  https://launchpad.net/ubuntu/+source/linux-snapdragon/4.15.0-1093.102
  https://launchpad.net/ubuntu/+source/linux-aws-hwe/4.15.0-1090.95~16.04.1
  https://launchpad.net/ubuntu/+source/linux-azure/4.15.0-1102.113~16.04.1
  https://launchpad.net/ubuntu/+source/linux-gcp/4.15.0-1090.103~16.04.1
  https://launchpad.net/ubuntu/+source/linux-hwe/4.15.0-128.131~16.04.1
  https://launchpad.net/ubuntu/+source/linux-oracle/4.15.0-1061.67~16.04.1