Description of problem:
The second part of the patch introduced in #131848 is bogous, more than that, it
introduce a real bug:

diff -ur iptables-1.2.11.orig/extensions/libipt_rpc.c
iptables-1.2.11/extensions/libipt_rpc.c
--- iptables-1.2.11.orig/extensions/libipt_rpc.c        2004-09-05
11:27:50.000000000 -0400
+++ iptables-1.2.11/extensions/libipt_rpc.c     2004-09-05 11:41:11.000000000 -0400
@@ -252,7 +252,7 @@

                        idup = 0;
                        memset(buf, 0, sizeof(buf));
-                       dst = (char *)buf - 1;
+                       dst = (char *)buf;
                }
        }


After dst = buf -1; dst is pointing to invalid memory, but there is a dst++ in
the for()-head before really accessing *dst -> no problem.

*with* this patch, we're accessing buf from [1] not from [0] when filling the
second parameter. But we're always parsing the buf from [0], and thus reading
invalid data.


Version-Release number of selected component (if applicable):
FC4 / iptables-1.3.0-2
(*really* tested with trustix 3.0 / iptables-1.3.3-2tr, while auditing the
iptables patches, which are the same as in FC4 package)

How reproducible:
everytime

Steps to Reproduce:
apply attached iptables-debug.patch to see the parsing results without the need
of a ipt_rpc.ko patched kernel. (The "No chain/target/match by that name" errors
came from kernel without a ipt_rpc.ko)

Actual results with bogous patch:
$ iptables -A INPUT -m rpc --rpcs mountd,1000,2000 -j DROP
parsing: 'mountd' -> 100005
parsing: '' -> 0
parsing: '' -> 0
iptables: No chain/target/match by that name

Expected results without bogous patch:
$ iptables -A INPUT -m rpc --rpcs mountd,1000,2000 -j DROP
parsing: 'mountd' -> 100005
parsing: '1000' -> 1000
parsing: '2000' -> 2000
iptables: No chain/target/match by that name

Additional info:
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=131848
https://lists.netfilter.org/pipermail/netfilter-devel/2004-September/016731.html