[USN-2908-4] Linux kernel regression

[Steve Beattie]

==========================================================================
Ubuntu Security Notice USN-2908-4
February 26, 2016

linux regression
==========================================================================

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

- Ubuntu 15.10

Summary:

USN-2908-1 introduced a regression in the Linux kernel.

Software Description:
- linux: Linux kernel

Details:

USN-2908-1 fixed vulnerabilities in the Linux kernel for Ubuntu
15.10. An incorrect locking fix caused a regression that broke
graphics displays for Ubuntu 15.10 guests running within VMWare
virtual machines. This update fixes the problem.

We apologize for the inconvenience.

Original advisory details:

 halfdog discovered that OverlayFS, when mounting on top of a FUSE mount,
 incorrectly propagated file attributes, including setuid. A local
 unprivileged attacker could use this to gain privileges. (CVE-2016-1576)
 
 halfdog discovered that OverlayFS in the Linux kernel incorrectly
 propagated security sensitive extended attributes, such as POSIX ACLs. A
 local unprivileged attacker could use this to gain privileges.
 (CVE-2016-1575)
 
 It was discovered that the Linux kernel did not properly enforce rlimits
 for file descriptors sent over UNIX domain sockets. A local attacker could
 use this to cause a denial of service. (CVE-2013-4312)
 
 It was discovered that the Linux kernel's Filesystem in Userspace (FUSE)
 implementation did not handle initial zero length segments properly. A
 local attacker could use this to cause a denial of service (unkillable
 task). (CVE-2015-8785)
 
 Andy Lutomirski discovered a race condition in the Linux kernel's
 translation lookaside buffer (TLB) handling of flush events. A local
 attacker could use this to cause a denial of service or possibly leak
 sensitive information. (CVE-2016-2069)

Update instructions:

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

Ubuntu 15.10:
  linux-image-4.2.0-30-generic    4.2.0-30.36
  linux-image-4.2.0-30-generic-lpae  4.2.0-30.36
  linux-image-4.2.0-30-lowlatency  4.2.0-30.36
  linux-image-4.2.0-30-powerpc-e500mc  4.2.0-30.36
  linux-image-4.2.0-30-powerpc-smp  4.2.0-30.36
  linux-image-4.2.0-30-powerpc64-emb  4.2.0-30.36
  linux-image-4.2.0-30-powerpc64-smp  4.2.0-30.36

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

References:
  http://www.ubuntu.com/usn/usn-2908-4
  http://www.ubuntu.com/usn/usn-2908-1
  https://launchpad.net/bugs/1548587

Package Information:
  https://launchpad.net/ubuntu/+source/linux/4.2.0-30.36

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