[USN-2843-1] Linux kernel vulnerabilities

[Steve Beattie]

==========================================================================
Ubuntu Security Notice USN-2843-1
December 17, 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:

Jan Beulich discovered that the KVM svm hypervisor implementation in the
Linux kernel did not properly catch Debug exceptions on AMD processors. An
attacker in a guest virtual machine could use this to cause a denial of
service (system crash) in the host OS. (CVE-2015-8104)

郭永刚 discovered that the ppp implementation in the Linux kernel did
not ensure that certain slot numbers are valid. A local attacker with the
privilege to call ioctl() on /dev/ppp could cause a denial of service
(system crash). (CVE-2015-7799)

Dmitry Vyukov discovered that the Linux kernel's keyring handler attempted
to garbage collect incompletely instantiated keys. A local unprivileged
attacker could use this to cause a denial of service (system crash).
(CVE-2015-7872)

It was discovered that the virtual video osd test driver in the Linux
kernel did not properly initialize data structures. A local attacker could
use this to obtain sensitive information from the kernel. (CVE-2015-7884)

It was discovered that the driver for Digi Neo and ClassicBoard devices did
not properly initialize data structures. A local attacker could use this to
obtain sensitive information from the kernel. (CVE-2015-7885)

Update instructions:

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

Ubuntu 15.10:
  linux-image-4.2.0-21-generic    4.2.0-21.25
  linux-image-4.2.0-21-generic-lpae  4.2.0-21.25
  linux-image-4.2.0-21-lowlatency  4.2.0-21.25
  linux-image-4.2.0-21-powerpc-e500mc  4.2.0-21.25
  linux-image-4.2.0-21-powerpc-smp  4.2.0-21.25
  linux-image-4.2.0-21-powerpc64-emb  4.2.0-21.25
  linux-image-4.2.0-21-powerpc64-smp  4.2.0-21.25

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. If
you use linux-restricted-modules, you have to update that package as
well to get modules which work with the new kernel version. Unless you
manually uninstalled the standard kernel metapackages (e.g. linux-generic,
linux-server, linux-powerpc), a standard system upgrade will automatically
perform this as well.

References:
  http://www.ubuntu.com/usn/usn-2843-1
  CVE-2015-7799, CVE-2015-7872, CVE-2015-7884, CVE-2015-7885,
  CVE-2015-8104

Package Information:
  https://launchpad.net/ubuntu/+source/linux/4.2.0-21.25

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