(RHSA-2015:1030) Important: kernel security and bug fix update

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

• A use-after-free flaw was found in the way the Linux kernel’s SCTP
  implementation handled authentication key reference counting during INIT
  collisions. A remote attacker could use this flaw to crash the system or,
  potentially, escalate their privileges on the system. (CVE-2015-1421,
  Important)

This issue was discovered by Sun Baoliang of Red Hat.

This update also fixes the following bugs:

• When ARP is disabled on an interface with an ARP entry for a neighbor
  host present in the ARP cache, letting the cached entry expire and
  attempting to communicate with that neighbor host could cause the host MAC
  address to not be resolved correctly after ARP is enabled again on the
  interface. With the following workaround, the entry is not expired and the
  described scenario works correctly:

1. Add the maximum number of ARP entries you expect for your configuration
   to the proc/sys/net/ipv4/neigh/default/gc_thresh file.

2. Ensure that relevant IP addresses are put in the ARP cache when the
   system boots, for example by executing the following two commands:

ping [IP address] -c 1
ifconfig ethX -arp

(BZ#1207350)

• Previously, the open() system call in some cases failed with an EBUSY
  error if the opened file was also being renamed at the same time. With this
  update, the kernel automatically retries open() when this failure occurs,
  and if the retry is not successful either, open() now fails with an ESTALE
  error. (BZ#1207813)

• Previously, a race condition occurred in the build_id_cache__add_s()
  function, which could truncate system files. A patch has been provided to
  fix this bug, and system files are no longer truncated in the
  aforementioned scenario. (BZ#1210591)

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.