(RHSA-2014:2023) 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.

It was found that the wordexp() function would perform command substitution
even when the WRDE_NOCMD flag was specified. An attacker able to provide
specially crafted input to an application using the wordexp() function, and
not sanitizing the input correctly, could potentially use this flaw to
execute arbitrary commands with the credentials of the user running that
application. (CVE-2014-7817)

This issue was discovered by Tim Waugh of the Red Hat Developer Experience
Team.

This update also fixes the following bug:

• Prior to this update, if a file stream that was opened in append mode and
  its underlying file descriptor were used at the same time and the file was
  truncated using the ftruncate() function on the file descriptor, a
  subsequent ftell() call on the stream incorrectly modified the file offset
  by seeking to the new end of the file. This update ensures that ftell()
  modifies the state of the file stream only when it is in append mode and
  its buffer is not empty. As a result, the described incorrect changes to
  the file offset no longer occur. (BZ#1170187)

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