RHSA-2015:1030 - Security Advisory

Topic

Updated kernel packages that fix one security issue and three bugs are now
available for Red Hat Enterprise Linux 6.4 Advanced Update Support.

Red Hat Product Security has rated this update as having Important security
impact. A Common Vulnerability Scoring System (CVSS) base score, which
gives a detailed severity rating, is available from the CVE link in the
References section.

Description

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.

Solution

Before applying this update, make sure all previously released errata
relevant to your system have been applied.

For details on how to apply this update, refer to:

https://access.redhat.com/articles/11258

Affected Products

• Red Hat Enterprise Linux Server - AUS 6.4 x86_64

Fixes

• BZ - 1196581 - CVE-2015-1421 kernel: net: slab corruption from use after free on INIT collisions

CVEs

• CVE-2015-1421

References

• https://access.redhat.com/security/updates/classification/#important