only start mountd if a non-commented line is in exports; decreased vulnerabilty in common cases

src/etc/rc

@@ -1,4 +1,4 @@
-#	$OpenBSD: rc,v 1.45 1997/09/02 14:49:25 kstailey Exp $
+#	$OpenBSD: rc,v 1.46 1997/09/14 10:35:40 deraadt Exp $
 
 # System startup script run by init on autoboot
 # or after single-user.
@@ -152,7 +152,8 @@ fi
 
 # $nfs_server is imported from /etc/netstart;
 # if $nfs_server == YES, the machine is setup for being an nfs server
-if [ X${nfs_server} = X"YES" -a -r /etc/exports ]; then
+if [ X${nfs_server} = X"YES" -a -r /etc/exports -a \
+    `cat /etc/exports | sed -e '/^#/d' | wc -l` -ne 0]; then
 	rm -f /var/db/mountdtab	
 	echo -n > /var/db/mountdtab
 	echo -n ' mountd';		mountd