USN-2851-1: Linux kernel vulnerabilities

Ubuntu Security Notice USN-2851-1

19th December, 2015

linux vulnerabilities

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

Ubuntu 15.10

Summary

Several security issues were fixed in the kernel.

Software description

linux
– Linux kernel

Details

Felix Wilhelm discovered a race condition in the Xen paravirtualized
drivers which can cause double fetch vulnerabilities. An attacker in the
paravirtualized guest could exploit this flaw to cause a denial of service
(crash the host) or potentially execute arbitrary code on the host.
(CVE-2015-8550)

Konrad Rzeszutek Wilk discovered the Xen PCI backend driver does not
perform sanity checks on the device's state. An attacker could exploit this
flaw to cause a denial of service (NULL dereference) on the host.
(CVE-2015-8551)

Konrad Rzeszutek Wilk discovered the Xen PCI backend driver does not
perform sanity checks on the device's state. An attacker could exploit this
flaw to cause a denial of service by flooding the logging system with
WARN() messages causing the initial domain to exhaust disk space.
(CVE-2015-8552)

Jann Horn discovered a ptrace issue with user namespaces in the Linux
kernel. The namespace owner could potentially exploit this flaw by ptracing
a root owned process entering the user namespace to elevate its privileges
and potentially gain access outside of the namespace.
(http://bugs.launchpad.net/bugs/1527374)

Update instructions

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

Ubuntu 15.10:: linux-image-4.2.0-22-powerpc64-smp

4.2.0-22.27; linux-image-4.2.0-22-lowlatency

4.2.0-22.27; linux-image-4.2.0-22-generic

4.2.0-22.27; linux-image-4.2.0-22-powerpc-e500mc

4.2.0-22.27; linux-image-4.2.0-22-powerpc-smp

4.2.0-22.27; linux-image-4.2.0-22-powerpc64-emb

4.2.0-22.27; linux-image-4.2.0-22-generic-lpae

4.2.0-22.27

To update your system, please follow these instructions:
https://wiki.ubuntu.com/Security/Upgrades.

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.