I noticed the following message from syslog: Jan 6 16:34:20 myserver login: FAILED LOGIN SESSION FROM xxx.edu FOR (null), Error in service module The '(null)' looks suspiciously to be a printout of a null string.
This also appears to happen with RH 6.1: Jan 17 11:02:22 mikrosopht PAM_pwdb[2396]: authentication failure; LOGIN(uid=0) -> valankar for login service Jan 17 11:02:23 mikrosopht login[2396]: FAILED LOGIN 1 FROM (null) FOR valankar, Authentication failure Jan 17 11:02:26 mikrosopht PAM_pwdb[2396]: (login) session opened for user valankar by LOGIN(uid=0)
This is normal behaviour when logging in from a local terminal. It is a NULL pointer and that's perfectly OK with printf...