(RHSA-2009:1672) 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 bug:

• a bug in the IPv6 implementation in the Linux kernel could have caused an
  unbalanced reference count. When using network bonding, this bug may have
  caused a hang when shutting the system down via “shutdown -h”, or prevented
  the network service from being stopped via “service network stop”.
  (BZ#538409)

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.