kernel security update

CentOS Errata and Security Advisory CESA-2014:0926

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

• A NULL pointer dereference flaw was found in the rds_iw_laddr_check()
  function in the Linux kernel’s implementation of Reliable Datagram Sockets
  (RDS). A local, unprivileged user could use this flaw to crash the system.
  (CVE-2014-2678, Moderate)

• It was found that the Xen hypervisor implementation did not properly
  clean memory pages previously allocated by the hypervisor. A privileged
  guest user could potentially use this flaw to read data relating to other
  guests or the hypervisor itself. (CVE-2014-4021, Moderate)

Red Hat would like to thank the Xen project for reporting CVE-2014-4021.
Upstream acknowledges Jan Beulich as the original reporter.

This update also fixes the following bugs:

• A bug in the journaling block device (jbd and jbd2) code could, under
  certain circumstances, trigger a BUG_ON() assertion and result in a kernel
  oops. This happened when an application performed an extensive number of
  commits to the journal of the ext3 file system and there was no currently
  active transaction while synchronizing the file’s in-core state. This
  problem has been resolved by correcting respective test conditions in the
  jbd and jbd2 code. (BZ#1097528)

• After a statically defined gateway became unreachable and its
  corresponding neighbor entry entered a FAILED state, the gateway stayed in
  the FAILED state even after it became reachable again. As a consequence,
  traffic was not routed through that gateway. This update allows probing
  such a gateway automatically so that the traffic can be routed through
  this gateway again once it becomes reachable. (BZ#1106354)

• Due to an incorrect condition check in the IPv6 code, the ipv6 driver
  was unable to correctly assemble incoming packet fragments, which resulted
  in a high IPv6 packet loss rate. This update fixes the said check for a
  fragment overlap and ensures that incoming IPv6 packet fragments are now
  processed as expected. (BZ#1107932)

• Recent changes in the d_splice_alias() function introduced a bug that
  allowed d_splice_alias() to return a dentry from a different directory
  than the directory being looked up. As a consequence in cluster
  environment, a kernel panic could be triggered when a directory was being
  removed while a concurrent cross-directory operation was performed on this
  directory on another cluster node. This update avoids the kernel panic in
  this situation by correcting the search logic in the d_splice_alias()
  function so that the function can no longer return a dentry from an
  incorrect directory. (BZ#1109720)

• The NFSv4 server did not handle multiple OPEN operations to the same file
  separately, which could cause the NFSv4 client to repeatedly send CLOSE
  requests with the same state ID, even though the NFS server rejected the
  request with an NFS4ERR_OLD_STATEID (10024) error code. This update
  ensures that the NFSv4 client no longer re-sends the same CLOSE request
  after receiving NFS4ERR_OLD_STATEID. (BZ#1113468)

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.

Merged security bulletin from advisories:
https://lists.centos.org/pipermail/centos-announce/2014-July/082605.html

Affected packages:
kernel
kernel-PAE
kernel-PAE-devel
kernel-debug
kernel-debug-devel
kernel-devel
kernel-doc
kernel-headers
kernel-xen
kernel-xen-devel

Upstream details at:
https://access.redhat.com/errata/RHSA-2014:0926