(RHSA-2011:1163) Important: kernel security and bug fix update

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

This update includes backported fixes for two security issues. These issues
only affected users of Red Hat Enterprise Linux 5.6 Extended Update
Support, as they have already been addressed for users of Red Hat
Enterprise Linux 5 in the 5.7 update, RHSA-2011:1065.

This update fixes the following security issues:

• A flaw was found in the way the Xen hypervisor implementation handled
  instruction emulation during virtual machine exits. A malicious user-space
  process running in an SMP guest could trick the emulator into reading a
  different instruction than the one that caused the virtual machine to exit.
  An unprivileged guest user could trigger this flaw to crash the host. This
  only affects systems with both an AMD x86 processor and the AMD
  Virtualization (AMD-V) extensions enabled. (CVE-2011-1780, Important)

• A flaw allowed the tc_fill_qdisc() function in the Linux kernel’s packet
  scheduler API implementation to be called on built-in qdisc structures. A
  local, unprivileged user could use this flaw to trigger a NULL pointer
  dereference, resulting in a denial of service. (CVE-2011-2525, Moderate)

This update also fixes the following bugs:

• A bug was found in the way the x86_emulate() function handled the IMUL
  instruction in the Xen hypervisor. On systems without support for hardware
  assisted paging (HAP), such as those running CPUs that do not have support
  for (or those that have it disabled) Intel Extended Page Tables (EPT) or
  AMD Virtualization (AMD-V) Rapid Virtualization Indexing (RVI), this bug
  could cause fully-virtualized guests to crash or lead to silent memory
  corruption. In reported cases, this issue occurred when booting
  fully-virtualized Red Hat Enterprise Linux 6.1 guests with memory cgroups
  enabled. (BZ#712884)

• A bug in the way the ibmvscsi driver handled interrupts may have
  prevented automatic path recovery for multipath devices. This bug only
  affected 64-bit PowerPC systems. (BZ#720929)

• The RHSA-2009:1243 update introduced a regression in the way file locking
  on NFS (Network File System) was handled. This caused applications to hang
  if they made a lock request on a file on an NFS version 2 or 3 file system
  that was mounted with the “sec=krb5” option. With this update, the original
  behavior of using mixed RPC authentication flavors for NFS and locking
  requests has been restored. (BZ#722854)

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