(RHSA-2012:0571) Moderate: kernel security and bug fix update

The kernel 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 the Linux kernel’s journal_unmap_buffer()
  function handled buffer head states. On systems that have an ext4 file
  system with a journal mounted, a local, unprivileged user could use this
  flaw to cause a denial of service. (CVE-2011-4086, Moderate)

• A flaw was found in the way the KVM_CREATE_IRQCHIP ioctl was handled.
  Calling this ioctl when at least one virtual CPU (VCPU) already existed
  could lead to a NULL pointer dereference later when the VCPU is scheduled
  to run. A local, unprivileged user on a KVM host could use this flaw to
  crash the host. (CVE-2012-1601, Moderate)

This update also fixes several bugs. Documentation for these changes will
be available shortly from the Technical Notes document linked to in the
References section.

Users should upgrade to these updated packages, which contain backported
patches to correct these issues, and fix the bugs noted in the Technical
Notes. The system must be rebooted for this update to take effect.