diff -up Linux-PAM-0.99.8.1/modules/pam_xauth/pam_xauth.c.no-free Linux-PAM-0.99.8.1/modules/pam_xauth/pam_xauth.c
--- Linux-PAM-0.99.8.1/modules/pam_xauth/pam_xauth.c.no-free	2007-09-21 16:02:06.000000000 +0200
+++ Linux-PAM-0.99.8.1/modules/pam_xauth/pam_xauth.c	2007-09-21 16:02:47.000000000 +0200
@@ -573,6 +573,7 @@ pam_sm_open_session (pam_handle_t *pamh,
 				   "can't set environment variable '%s'",
 				   xauthority);
 		putenv (xauthority); /* The environment owns this string now. */
+		xauthority = NULL;
 
 		/* set $DISPLAY in pam handle to make su - work */
 		{