From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2D118C48BD1 for ; Fri, 11 Jun 2021 12:52:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 07B8A613B8 for ; Fri, 11 Jun 2021 12:52:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230349AbhFKMys (ORCPT ); Fri, 11 Jun 2021 08:54:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33040 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230233AbhFKMys (ORCPT ); Fri, 11 Jun 2021 08:54:48 -0400 Received: from orbyte.nwl.cc (orbyte.nwl.cc [IPv6:2001:41d0:e:133a::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7DFFDC061574 for ; Fri, 11 Jun 2021 05:52:50 -0700 (PDT) Received: from n0-1 by orbyte.nwl.cc with local (Exim 4.94.2) (envelope-from ) id 1lrgeW-0003e5-Dn; Fri, 11 Jun 2021 14:52:48 +0200 Date: Fri, 11 Jun 2021 14:52:48 +0200 From: Phil Sutter To: Pablo Neira Ayuso Cc: netfilter-devel@vger.kernel.org, Florian Westphal Subject: Re: [nf-next PATCH] netfilter: nft_exthdr: Search chunks in SCTP packets only Message-ID: <20210611125248.GL22614@orbyte.nwl.cc> Mail-Followup-To: Phil Sutter , Pablo Neira Ayuso , netfilter-devel@vger.kernel.org, Florian Westphal References: <20210610142316.24354-1-phil@nwl.cc> <20210610174334.GA24536@salvia> <20210611102624.GI22614@orbyte.nwl.cc> <20210611115654.GA6356@salvia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210611115654.GA6356@salvia> Sender: Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org On Fri, Jun 11, 2021 at 01:56:54PM +0200, Pablo Neira Ayuso wrote: > On Fri, Jun 11, 2021 at 12:26:24PM +0200, Phil Sutter wrote: > > On Thu, Jun 10, 2021 at 07:43:34PM +0200, Pablo Neira Ayuso wrote: > > > On Thu, Jun 10, 2021 at 04:23:16PM +0200, Phil Sutter wrote: > > > > Since user space does not generate a payload dependency, plain sctp > > > > chunk matches cause searching in non-SCTP packets, too. Avoid this > > > > potential mis-interpretation of packet data by checking pkt->tprot. > > > > > > > > Fixes: 133dc203d77df ("netfilter: nft_exthdr: Support SCTP chunks") > > > > Signed-off-by: Phil Sutter > > > > --- > > > > net/netfilter/nft_exthdr.c | 5 ++++- > > > > 1 file changed, 4 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/net/netfilter/nft_exthdr.c b/net/netfilter/nft_exthdr.c > > > > index 7f705b5c09de8..1093bb83f8aeb 100644 > > > > --- a/net/netfilter/nft_exthdr.c > > > > +++ b/net/netfilter/nft_exthdr.c > > > > @@ -312,6 +312,9 @@ static void nft_exthdr_sctp_eval(const struct nft_expr *expr, > > > > const struct sctp_chunkhdr *sch; > > > > struct sctp_chunkhdr _sch; > > > > > > > > + if (!pkt->tprot_set || pkt->tprot != IPPROTO_SCTP) > > > > + goto err; > > > > > > nft_set_pktinfo_unspec() already initializes pkt->tprot to zero. > > > > > > I think it's safe to simplify this to: > > > > > > if (pkt->tprot != IPPROTO_SCTP) > > > > Are you sure? Checking the spots that (should) initialize > > tprot/tprot_set, in nft_do_chain_inet() it seems that if state->pf is > > neither NFPROTO_IPV4 nor NFPROTO_IPV6, nft_do_chain() is called without > > prior init. Maybe default case should call nft_set_pktinfo_unspec()? > > state->pf in nft_do_chain_inet() can only be either NFPROTO_IPV4 or > NFPROTO_IPV6. Shouldn't there be a WARN_ON_ONCE or something in the default case then? Looking at nf_hook(), it seems entirely possible to me that state->pf might be NFPROTO_ARP, for instance. That's probably just me not getting it, but things we rely upon shouldn't be hidden that well, right? > pkt->tprot_set is there to deal with a corner case: IPPROTO_IP (0). > If pkt->tprot_set == true and pkt->tprot == 0, it means: "match on > IPPROTO_IP". For other IPPROTO_*, checking pkt->tprot looks safe to me. Ah, thanks for clarifying! So whenever I check a specific value that's non-zero, tprot_set doesn't matter. Should I send a patch for the same change in nft_tcp_header_pointer(), too? (That's where I copied the code from. ;) > > BTW: The final return call in nft_do_chain_inet_ingress() is dead code, > > right? > > You mean the default case of nft_do_chain_inet_ingress()? inet/ingress > is special, it allows you to filter IPv4 and IPv6 traffic only. > Anything else from ingress is accepted (you should filter it via > netdev family). Oh, sorry. Looks like I had tomatoes on the eyes[1]: I missed that the non-default cases just 'break' and therefore hit the function's last line. Thanks, Phil [1] Famous German idiom.