This bug has been copied from bug #750149 and has been proposed to be backported to 5.8 z-stream (EUS).
http://gerrit.virt.bos.redhat.com/gerrit/47
Technical note added. If any revisions are required, please edit the "Technical Notes" field accordingly. All revisions will be proofread by the Engineering Content Services team. New Contents: Attempts to change the root user's password would result in a "device busy" error on the "/etc/shadow/" file. This occurred because multipathd held a lock on the file. The script that changes the password now restarts multipathd to release the lock, avoiding the "device busy" error.
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. http://rhn.redhat.com/errata/RHBA-2012-0367.html