(RHSA-2013:0622) Important: kernel-rt security and bug fix update

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

This update fixes the following security issues:

• A flaw was found in the way file permission checks for the
  “/dev/cpu/[x]/msr” files were performed in restricted root environments
  (for example, when using a capability-based security model). A local user
  with the ability to write to these files could use this flaw to escalate
  their privileges to kernel level, for example, by writing to the
  SYSENTER_EIP_MSR register. (CVE-2013-0268, Important)

• A race condition was found in the way the Linux kernel’s ptrace
  implementation handled PTRACE_SETREGS requests when the debuggee was woken
  due to a SIGKILL signal instead of being stopped. A local, unprivileged
  user could use this flaw to escalate their privileges. (CVE-2013-0871,
  Important)

• An out-of-bounds access flaw was found in the way SOCK_DIAG_BY_FAMILY
  Netlink messages were processed in the Linux kernel. A local, unprivileged
  user could use this flaw to escalate their privileges. (CVE-2013-1763,
  Important)

• It was found that the default SCSI command filter does not accommodate
  commands that overlap across device classes. A privileged guest user could
  potentially use this flaw to write arbitrary data to a LUN that is
  passed-through as read-only. (CVE-2012-4542, Moderate)

• A flaw was found in the way the __skb_recv_datagram() function in the
  Linux kernel processed payload-less socket buffers (skb) when the MSG_PEEK
  option was requested. A local, unprivileged user could use this flaw to
  cause a denial of service (infinite loop). (CVE-2013-0290, Moderate)

The CVE-2012-4542 issue was discovered by Paolo Bonzini of Red Hat.

This update also fixes the following bugs:

• There was high contention on run-queue lock when load balancing before
  idling, causing latency spikes on high CPU core count systems. With this
  update, IPI is used to send notification to cores with pending work, and
  the cores push the work rather than trying to pull it, resolving this
  issue. (BZ#858396)

• Previously, ACPI lock was converted to an rt_mutex, leading to a
  traceback when scheduling while atomic. With this update, ACPI lock has
  been converted back to a raw spinlock. (BZ#909965)

• Fibre Channel (FC)/iSCSI device state was set to off-line and after a
  timeout, not set back to running. Such a device would not come back online
  after a fast_io_fail or timeout. With this update, an explicit check for
  the device being offline has been added, and the device is set back to
  running when re-initializing, allowing devices to recover after a failure
  or timeout. (BZ#912942)

Users should upgrade to these updated packages, which correct these issues.
The system must be rebooted for this update to take effect.