netfilter: xt_connbytes: handle negation correctly

"! --connbytes 23:42" should match if the packet/byte count is not in range.

As there is no explict "invert match" toggle in the match structure,
userspace swaps the from and to arguments
(i.e., as if "--connbytes 42:23" were given).

However, "what <= 23 && what >= 42" will always be false.

Change things so we use "||" in case "from" is larger than "to".

This change may look like it breaks backwards compatibility when "to" is 0.
However, older iptables binaries will refuse "connbytes 42:0",
and current releases treat it to mean "! --connbytes 0:42",
so we should be fine.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/netfilter/xt_connbytes.c b/net/netfilter/xt_connbytes.c
index 5b138506690ec578105911ffb64309b5297d6458..9ddf1c3bfb39c5f67cb8f8c24ccdd22d03c38f10 100644 (file)
--- a/net/netfilter/xt_connbytes.c
+++ b/net/netfilter/xt_connbytes.c
@@ -87,10 +87,10 @@ connbytes_mt(const struct sk_buff *skb, struct xt_action_param *par)
                break;
        }
 
-       if (sinfo->count.to)
+       if (sinfo->count.to >= sinfo->count.from)
                return what <= sinfo->count.to && what >= sinfo->count.from;
-       else
-               return what >= sinfo->count.from;
+       else /* inverted */
+               return what < sinfo->count.to || what > sinfo->count.from;
 }
 
 static int connbytes_mt_check(const struct xt_mtchk_param *par)