[patch]run ipfw2 with incomplete options will make a coredump

[Kang Liu]

>Submitter-Id:	current-users
>Originator:	Kang Liu
>Organization:	Beijing University of Technology
>Confidential:	no
>Synopsis:	[patch]run ipfw2 with incomplete options will make a coredump
>Severity:	critical
>Priority:	high
>Category:	bin
>Class:		sw-bug
>Release:	FreeBSD 4.9-PRERELEASE i386
>Environment:
System: FreeBSD cnproxy.bjpu.edu.cn 4.9-PRERELEASE FreeBSD 4.9-PRERELEASE #33: Sun Aug 31 15:58:08 CST 2003
root at cnproxy.bjpu.edu.cn:/usr/obj/usr/src/sys/CNPROXY i386
>Description:
run ipfw2 enable/disable with incomplete options will make a coredump with signal 10.
this problem can be reproduced on the latest 5.1current, I do not have a 4.8 running ipfw2, 
but I think -stable with ipfw2 may have the same problem.
The src has been freezed for 4.9, but this problem is so serious, Can anyone test and commit it?
>How-To-Repeat:
on a latest 5.1 machine,run:
# ipfw disable (or ipfw enable)
Bus error (core dumped)

a ipfw.core would be produced

In /var/log/message:
date time hosename kernel: pid num (ipfw), uid 0: exited on signal 10 (core dumped)

>Fix:
I think a better way is to check "ac" instead of check "av".

--- ipfw2.c.orig	Tue Sep  2 12:54:28 2003
+++ ipfw2.c	Tue Sep  2 12:54:54 2003
@@ -1643,7 +1643,7 @@
 	ac--;
 	av++;
 
-	if (*av == NULL) {
+	if (ac == 0) {
 		warnx("missing keyword to enable/disable\n");
 	} else if (strncmp(*av, "firewall", strlen(*av)) == 0) {
 		sysctlbyname("net.inet.ip.fw.enable", NULL, 0,