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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 15C0DC47082 for ; Tue, 8 Jun 2021 10:17:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DEE7661185 for ; Tue, 8 Jun 2021 10:17:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229937AbhFHKSv (ORCPT ); Tue, 8 Jun 2021 06:18:51 -0400 Received: from mail.netfilter.org ([217.70.188.207]:56124 "EHLO mail.netfilter.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229626AbhFHKSv (ORCPT ); Tue, 8 Jun 2021 06:18:51 -0400 Received: from netfilter.org (unknown [90.77.255.23]) by mail.netfilter.org (Postfix) with ESMTPSA id B8DF763E3D; Tue, 8 Jun 2021 12:15:45 +0200 (CEST) Date: Tue, 8 Jun 2021 12:16:55 +0200 From: Pablo Neira Ayuso To: Florian Westphal Cc: Phil Sutter , netfilter-devel@vger.kernel.org Subject: Re: [nf-next PATCH v2] netfilter: nft_exthdr: Fix for unsafe packet data read Message-ID: <20210608101655.GA16424@salvia> References: <20210608094057.24598-1-phil@nwl.cc> <20210608095621.GA15808@salvia> <20210608100754.GG20020@breakpoint.cc> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20210608100754.GG20020@breakpoint.cc> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org On Tue, Jun 08, 2021 at 12:07:54PM +0200, Florian Westphal wrote: > Pablo Neira Ayuso wrote: > > On Tue, Jun 08, 2021 at 11:40:57AM +0200, Phil Sutter wrote: > > > While iterating through an SCTP packet's chunks, skb_header_pointer() is > > > called for the minimum expected chunk header size. If (that part of) the > > > skbuff is non-linear, the following memcpy() may read data past > > > temporary buffer '_sch'. Use skb_copy_bits() instead which does the > > > right thing in this situation. > > > > > > Fixes: 133dc203d77df ("netfilter: nft_exthdr: Support SCTP chunks") > > > Suggested-by: Florian Westphal > > > Signed-off-by: Phil Sutter > > > --- > > > Changes since v1: > > > - skb_copy_bits() call error handling added > > > --- > > > net/netfilter/nft_exthdr.c | 4 +++- > > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > > > diff --git a/net/netfilter/nft_exthdr.c b/net/netfilter/nft_exthdr.c > > > index 1b0579cb62d08..7f705b5c09de8 100644 > > > --- a/net/netfilter/nft_exthdr.c > > > +++ b/net/netfilter/nft_exthdr.c > > > @@ -327,7 +327,9 @@ static void nft_exthdr_sctp_eval(const struct nft_expr *expr, > > > break; > > > > > > dest[priv->len / NFT_REG32_SIZE] = 0; > > > - memcpy(dest, (char *)sch + priv->offset, priv->len); > > > + if (skb_copy_bits(pkt->skb, offset + priv->offset, > > > + dest, priv->len) < 0) > > > + break; > > > > Hm, it looks like tcp exthdt matching has the same problem? > > Tcp exthdr either copies from skb linear area or a on-stack scratch space, > it looks ok to me. Indeed, I overlook the nft_tcp_header_pointer() call a few lines before.