(RHSA-2009:1587) 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 issues:

• a system with SELinux enforced was more permissive in allowing local
  users in the unconfined_t domain to map low memory areas even if the
  mmap_min_addr restriction was enabled. This could aid in the local
  exploitation of NULL pointer dereference bugs. (CVE-2009-2695, Important)

• a NULL pointer dereference flaw was found in each of the following
  functions in the Linux kernel: pipe_read_open(), pipe_write_open(), and
  pipe_rdwr_open(). When the mutex lock is not held, the i_pipe pointer could
  be released by other processes before it is used to update the pipe’s
  reader and writer counters. This could lead to a local denial of service or
  privilege escalation. (CVE-2009-3547, Important)

This update also fixes the following bugs:

• a caching bug in nfs_readdir() has been resolved. This may have caused
  parts of directory listings to become stale, as they came from cached data
  when they should not have, possibly causing NFS clients to see duplicate
  files or not see all files in a directory. (BZ#526959)

• a bug prevented the pciehp driver from detecting PCI Express hot plug
  slots on some systems. (BZ#530381)

• when a process attempted to read from a page that had first been accessed
  by writing to part of it (via write(2)), the NFS client needed to flush the
  modified portion of the page out to the server, and then read the entire
  page back in. This flush caused performance issues. (BZ#521243)

• a deadlock was found in the cciss driver. In rare cases, this caused an
  NMI lockup during boot. Messages such as “cciss: controller cciss[x]
  failed, stopping.” and “cciss[x]: controller not responding.” may have been
  displayed on the console. (BZ#525728)

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.