(RHSA-2015:0863) Moderate: glibc security and bug fix update

The glibc packages provide the standard C libraries (libc), POSIX thread
libraries (libpthread), standard math libraries (libm), and the Name
Server Caching Daemon (nscd) used by multiple programs on the system.
Without these libraries, the Linux system cannot function correctly.

A buffer overflow flaw was found in the way glibc’s gethostbyname_r() and
other related functions computed the size of a buffer when passed a
misaligned buffer as input. An attacker able to make an application call
any of these functions with a misaligned buffer could use this flaw to
crash the application or, potentially, execute arbitrary code with the
permissions of the user running the application. (CVE-2015-1781)

It was discovered that, under certain circumstances, glibc’s getaddrinfo()
function would send DNS queries to random file descriptors. An attacker
could potentially use this flaw to send DNS queries to unintended
recipients, resulting in information disclosure or data loss due to the
application encountering corrupted data. (CVE-2013-7423)

The CVE-2015-1781 issue was discovered by Arjun Shankar of Red Hat.

This update also fixes the following bug:

• Previously, the nscd daemon did not properly reload modified data when
  the user edited monitored nscd configuration files. As a consequence, nscd
  returned stale data to system processes. This update adds a system of
  inotify-based monitoring and stat-based backup monitoring for nscd
  configuration files. As a result, nscd now detects changes to its
  configuration files and reloads the data properly, which prevents it from
  returning stale data. (BZ#1194149)

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