It's not kernel problem. There are two problem, rusers and libc.
I'm using rusers of NetKit-B-0.06 and libc-5.3.5.
Here is a patch for rusers.
I'll send you another patch for libc later.
-- NIIBE Yutaka================= --- rusers/rnusers_xdr.c~ +++ rusers/rnusers_xdr.c @@ -14,22 +14,18 @@ XDR *xdrs; struct ru_utmp *objp; { - char *ptr; int size; - ptr = objp->ut_line; size = sizeof(objp->ut_line); - if (!xdr_bytes(xdrs, &ptr, &size, size)) { + if (!xdr_bytes(xdrs, &objp->ut_line, &size, size)) { return (FALSE); } - ptr = objp->ut_name; size = sizeof(objp->ut_line); - if (!xdr_bytes(xdrs, &ptr, &size, size)) { + if (!xdr_bytes(xdrs, &objp->ut_name, &size, size)) { return (FALSE); } - ptr = objp->ut_host; size = sizeof(objp->ut_host); - if (!xdr_bytes(xdrs, &ptr, &size, size)) { + if (!xdr_bytes(xdrs, &objp->ut_host, &size, size)) { return (FALSE); } if (!xdr_long(xdrs, &objp->ut_time)) { =================