Moderate: glibc security and bug fix update

Updated glibc packages that fix one security issue and three bugs are now
available for Red Hat Enterprise Linux 6.

The Red Hat Security Response Team has rated this update as having moderate
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.

The glibc packages provide the standard C and standard math libraries used
by multiple programs on the system. Without these libraries, the Linux
system cannot function correctly.

An integer overflow flaw was found in the implementation of the printf
functions family. This could allow an attacker to bypass FORTIFY_SOURCE
protections and execute arbitrary code using a format string flaw in
an application, even though these protections are expected to limit the
impact of such flaws to an application abort. (CVE-2012-0864)

This update also fixes the following bugs:

* Previously, the dynamic loader generated an incorrect ordering for
initialization according to the ELF specification. This could result in
incorrect ordering of DSO constructors and destructors. With this update,
dependency resolution has been fixed. (BZ#783999)

* Previously, locking of the main malloc arena was incorrect in the retry
path. This could result in a deadlock if an sbrk request failed. With this
update, locking of the main arena in the retry path has been fixed. This
issue was exposed by a bug fix provided in the RHSA-2012:0058 update.
(BZ#795328)

* Calling memcpy with overlapping arguments on certain processors would
generate unexpected results. While such code is a clear violation of
ANSI/ISO standards, this update restores prior memcpy behavior. (BZ#799259)

All users of glibc are advised to upgrade to these updated packages, which
contain patches to resolve these issues.

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

This update is available via the Red Hat Network. Details on how to
use the Red Hat Network to apply this update are available at
https://access.redhat.com/knowledge/articles/11258

794766 - CVE-2012-0864 glibc: FORTIFY_SOURCE format string protection bypass via "nargs" integer overflow
799259 - Change in memcpy behavior for overlapping arguments breaks existing applications

https://www.redhat.com/security/data/cve/CVE-2012-0864.html
https://access.redhat.com/security/updates/classification/#moderate
https://rhn.redhat.com/errata/RHSA-2012-0058.html