(RHSA-2014:1943) Moderate: kernel-rt security, bug fix, and enhancement update

The kernel-rt packages contain the Linux kernel, the core of any Linux
operating system.

A denial of service flaw was found in the way the Linux kernel’s XFS file
system implementation ordered directory hashes under certain conditions.
A local attacker could use this flaw to corrupt the file system by creating
directories with colliding hash values, potentially resulting in a system
crash. (CVE-2014-7283, Moderate)

An out-of-bounds memory access flaw was found in the syscall tracing
functionality of the Linux kernel’s perf subsystem. A local, unprivileged
user could use this flaw to crash the system. (CVE-2014-7825, Moderate)

An out-of-bounds memory access flaw was found in the syscall tracing
functionality of the Linux kernel’s ftrace subsystem. On a system with
ftrace syscall tracing enabled, a local, unprivileged user could use this
flaw to crash the system, or escalate their privileges. (CVE-2014-7826,
Moderate)

Red Hat would like to thank Robert Święcki for reporting CVE-2014-7825 and
CVE-2014-7826.

The kernel-rt packages have been upgraded to upstream version 3.10.58,
which provides a number of bug fixes and enhancements over the previous
version. (BZ#1158105)

This update also fixes the following bugs:

• Automatic NUMA balancing on a low priority thread could cause memory
  contention with a high priority thread running in the same process.
  This contention could trigger poor realtime performance on the system.
  In order to avoid this potential memory contention, the MRG Realtime kernel
  now disables NUMA_BALANCING_DEFAULT_ENABLED. (BZ#1158940)

• When tracing a bug, WARN*() functions could flood the ring buffer making
  the trace useless or even overflowing the ring buffer. To address this
  issue, a traceoff_on_warning option was added to the kernel command line
  and as a sysctl option. This option disables the writing of the warning
  messages to the ring buffer, which results in a cleaner trace for
  debugging. (BZ#1155200)

In addition, this update adds the following enhancement:

• Support for XHCI (USB 3) is now enabled in the MRG Realtime kernel.
  (BZ#1134095)

All kernel-rt users are advised to upgrade to these updated packages, which
contain correct these issues and add these enhancements. The system must be
rebooted for this update to take effect.