(RHSA-2010:0893) Important: 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 issue:

• Buffer overflow flaws were found in the Linux kernel’s implementation of
  the server-side External Data Representation (XDR) for the Network File
  System (NFS) version 4. An attacker on the local network could send a
  specially-crafted large compound request to the NFSv4 server, which could
  possibly result in a kernel panic (denial of service) or, potentially, code
  execution. (CVE-2010-2521, Important)

This update also fixes the following bugs:

• A race condition existed when generating new process IDs with the result
  that the wrong process could have been signaled or killed accidentally,
  leading to various application faults. This update detects and disallows
  the reuse of PID numbers. (BZ#638864)

• When multiple JBD-based (Journaling Block Device) file systems were
  mounted concurrently, and no other JBD-based file systems were already
  mounted, a race could occur between JBD slab cache creation and deletion.
  (BZ#645653)

• A missing memory barrier caused a race condition in the AIO subsystem
  between the read_events() and aio_complete() functions. This may have
  caused a thread in read_events() to sleep indefinitely, possibly causing an
  application hang. (BZ#638868)

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