A Linux kernel security update has been released for Ubuntu Linux 14.04 ESM and 16.04 LTS.

USN-4904-1: Linux kernel vulnerabilities

==========================================================================
Ubuntu Security Notice USN-4904-1
April 13, 2021

linux, linux-aws, linux-kvm, linux-lts-xenial, linux-raspi2,
linux-snapdragon vulnerabilities
==========================================================================

A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 16.04 LTS
- Ubuntu 14.04 ESM

Summary:

Several security issues were fixed in the Linux kernel.

Software Description:
- linux: Linux kernel
- linux-aws: Linux kernel for Amazon Web Services (AWS) systems
- linux-kvm: Linux kernel for cloud environments
- linux-raspi2: Linux kernel for Raspberry Pi (V8) systems
- linux-snapdragon: Linux kernel for Qualcomm Snapdragon processors
- linux-lts-xenial: Linux hardware enablement kernel from Xenial for Trusty

Details:

Ben Harris discovered that the Linux kernel would strip extended privilege
attributes of files when performing a failed unprivileged system call. A
local attacker could use this to cause a denial of service. (CVE-2015-1350)

Andrey Konovalov discovered that the video4linux driver for Hauppauge HD
PVR USB devices in the Linux kernel did not properly handle some error
conditions. A physically proximate attacker could use this to cause a
denial of service (system crash) or possibly execute arbitrary code.
(CVE-2017-16644)

It was discovered that the timer stats implementation in the Linux kernel
allowed the discovery of a real PID value while inside a PID namespace. A
local attacker could use this to expose sensitive information.
(CVE-2017-5967)

Wen Xu discovered that the xfs file system implementation in the Linux
kernel did not properly validate the number of extents in an inode. An
attacker could use this to construct a malicious xfs image that, when
mounted, could cause a denial of service (system crash). (CVE-2018-13095)

It was discovered that the Fujitsu ES network device driver for the Linux
kernel did not properly check for errors in some situations, leading to a
NULL pointer dereference. A local attacker could use this to cause a denial
of service. (CVE-2019-16231)

It was discovered that the Marvell 8xxx Libertas WLAN device driver in the
Linux kernel did not properly check for errors in certain situations,
leading to a NULL pointer dereference. A local attacker could possibly use
this to cause a denial of service. (CVE-2019-16232)

It was discovered that the ADIS16400 IIO IMU Driver for the Linux kernel
did not properly deallocate memory in certain error conditions. A local
attacker could use this to cause a denial of service (memory exhaustion).
(CVE-2019-19061)

It was discovered that a race condition existed in the floppy device driver
in the Linux kernel. An attacker with access to the floppy device could use
this to cause a denial of service (system crash) or possibly execute
arbitrary code. (CVE-2021-20261)

Olivier Benjamin, Norbert Manthey, Martin Mazein, and Jan H. Schönherr
discovered that the Xen paravirtualization bckend in the Linux kernel did
not properly propagate errors to frontend drivers in some situations. An
attacker in a guest VM could possibly use this to cause a denial of service
(host domain crash). (CVE-2021-26930)

Jan Beulich discovered that multiple Xen backends in the Linux kernel did
not properly handle certain error conditions under paravirtualization. An
attacker in a guest VM could possibly use this to cause a denial of service
(host domain crash). (CVE-2021-26931)

Jan Beulich discovered that the Xen netback backend in the Linux kernel did
not properly handle certain error conditions under paravirtualization. An
attacker in a guest VM could possibly use this to cause a denial of service
(host domain crash). (CVE-2021-28038)

Update instructions:

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

Ubuntu 16.04 LTS:
linux-image-4.4.0-1091-kvm 4.4.0-1091.100
linux-image-4.4.0-1126-aws 4.4.0-1126.140
linux-image-4.4.0-1150-raspi2 4.4.0-1150.161
linux-image-4.4.0-1154-snapdragon 4.4.0-1154.164
linux-image-4.4.0-208-generic 4.4.0-208.240
linux-image-4.4.0-208-generic-lpae 4.4.0-208.240
linux-image-4.4.0-208-lowlatency 4.4.0-208.240
linux-image-4.4.0-208-powerpc-e500mc 4.4.0-208.240
linux-image-4.4.0-208-powerpc-smp 4.4.0-208.240
linux-image-4.4.0-208-powerpc64-emb 4.4.0-208.240
linux-image-4.4.0-208-powerpc64-smp 4.4.0-208.240
linux-image-aws 4.4.0.1126.131
linux-image-generic 4.4.0.208.214
linux-image-generic-lpae 4.4.0.208.214
linux-image-kvm 4.4.0.1091.89
linux-image-lowlatency 4.4.0.208.214
linux-image-powerpc-e500mc 4.4.0.208.214
linux-image-powerpc-smp 4.4.0.208.214
linux-image-powerpc64-emb 4.4.0.208.214
linux-image-powerpc64-smp 4.4.0.208.214
linux-image-raspi2 4.4.0.1150.150
linux-image-snapdragon 4.4.0.1154.146
linux-image-virtual 4.4.0.208.214

Ubuntu 14.04 ESM:
linux-image-4.4.0-1090-aws 4.4.0-1090.94
linux-image-4.4.0-208-generic 4.4.0-208.240~14.04.1
linux-image-4.4.0-208-generic-lpae 4.4.0-208.240~14.04.1
linux-image-4.4.0-208-lowlatency 4.4.0-208.240~14.04.1
linux-image-aws 4.4.0.1090.87
linux-image-generic-lpae-lts-xenial 4.4.0.208.181
linux-image-generic-lts-xenial 4.4.0.208.181
linux-image-lowlatency-lts-xenial 4.4.0.208.181
linux-image-virtual-lts-xenial 4.4.0.208.181

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://ubuntu.com/security/notices/USN-4904-1
CVE-2015-1350, CVE-2017-16644, CVE-2017-5967, CVE-2018-13095,
CVE-2019-16231, CVE-2019-16232, CVE-2019-19061, CVE-2021-20261,
CVE-2021-26930, CVE-2021-26931, CVE-2021-28038

Package Information:
  https://launchpad.net/ubuntu/+source/linux/4.4.0-208.240
  https://launchpad.net/ubuntu/+source/linux-aws/4.4.0-1126.140
  https://launchpad.net/ubuntu/+source/linux-kvm/4.4.0-1091.100
  https://launchpad.net/ubuntu/+source/linux-raspi2/4.4.0-1150.161
  https://launchpad.net/ubuntu/+source/linux-snapdragon/4.4.0-1154.164