(RHSA-2015:1042) Important: kernel security and bug fix update

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

• It was found that the Linux kernel’s implementation of vectored pipe read
  and write functionality did not take into account the I/O vectors that were
  already processed when retrying after a failed atomic access operation,
  potentially resulting in memory corruption due to an I/O vector array
  overrun. A local, unprivileged user could use this flaw to crash the system
  or, potentially, escalate their privileges on the system. (CVE-2015-1805,
  Important)

The security impact of this issue was discovered by Red Hat.

This update fixes the following bugs:

• Due to a bug in the lpfc_device_reset_handler() function, a scsi command
  timeout could lead to a system crash. With this update,
  lpfc_device_reset_handler recovers storage without crashing. (BZ#1070964)

• Due to the code decrementing the reclaim_in_progress counter without
  having incremented it first, severe spinlock contention occurred in the
  shrink_zone() function even though the vm.max_reclaims_in_progress feature
  was set to 1. This update provides a patch fixing the underlying source
  code, and spinlock contention no longer occurs in this scenario.
  (BZ#1164105)

• A TCP socket using SACK that had a retransmission but recovered from it,
  failed to reset the retransmission timestamp. As a consequence, on certain
  connections, if a packet had to be re-transmitted, the retrans_stamp
  variable was only cleared when the next acked packet was received.
  This could lead to an early abortion of the TCP connection if this next
  packet also got lost. With this update, the socket clears retrans_stamp
  when the recovery is completed, thus fixing the bug. (BZ#1205521)

• Previously, the signal delivery paths did not clear the TS_USEDFPU flag,
  which could cause problems in the switch_to() function and lead to
  floating-point unit (FPU) corruption. With this update, TS_USEDFPU is
  cleared as expected, and FPU is no longer under threat of corruption.
  (BZ#1193505)

• A race condition in the exit_sem() function previously caused the
  semaphore undo list corruption. As a consequence, a kernel crash could
  occur. The corruption in the semaphore undo list has been fixed, and the
  kernel no longer crashes in this situation. (BZ#1124574)

• Previously, when running the “virsh blockresize [Device] [Newsize]”
  command to resize the disk, the new size was not reflected in a Red Hat
  Enterprise Linux 5 Virtual Machine (VM). With this update, the new size is
  now reflected online immediately in a Red Hat Enterprise Linux 5 VM so it
  is no longer necessary to reboot the VM to see the new disk size.
  (BZ#1200855)

All kernel users are advised to upgrade to these updated packages, which
contain backported patches to correct these issues. The system must be
rebooted for this update to take effect.