--- libaitsess/src/sess.c	2011/09/07 21:06:56	1.3.2.3
+++ libaitsess/src/sess.c	2011/09/07 21:37:23	1.3.2.4
@@ -3,7 +3,7 @@
 *  by Michael Pounov <misho@openbsd-bg.org>
 *
 * $Author: misho $
-* $Id: sess.c,v 1.3.2.3 2011/09/07 21:06:56 misho Exp $
+* $Id: sess.c,v 1.3.2.4 2011/09/07 21:37:23 misho Exp $
 *
 **************************************************************************
 The ELWIX and AITNET software is distributed under the following
@@ -338,6 +338,10 @@ sess_prepareSession(tagSess * __restrict s, u_char use
 	assert(s);
 	if (!s) {
 		sess_SetErr(EINVAL, "Error:: invalid argument\n");
+		return NULL;
+	}
+	if (s->addr) {
+		sess_SetErr(EINVAL, "Error:: already attached memory\n");
 		return NULL;
 	}