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 4002AC4743E for ; Tue, 8 Jun 2021 10:07:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2050C61246 for ; Tue, 8 Jun 2021 10:07:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231171AbhFHKJt (ORCPT ); Tue, 8 Jun 2021 06:09:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57920 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231320AbhFHKJt (ORCPT ); Tue, 8 Jun 2021 06:09:49 -0400 Received: from Chamillionaire.breakpoint.cc (Chamillionaire.breakpoint.cc [IPv6:2a0a:51c0:0:12e:520::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6347AC061574 for ; Tue, 8 Jun 2021 03:07:56 -0700 (PDT) Received: from fw by Chamillionaire.breakpoint.cc with local (Exim 4.92) (envelope-from ) id 1lqYeI-00004u-L8; Tue, 08 Jun 2021 12:07:54 +0200 Date: Tue, 8 Jun 2021 12:07:54 +0200 From: Florian Westphal To: Pablo Neira Ayuso Cc: Phil Sutter , netfilter-devel@vger.kernel.org, Florian Westphal Subject: Re: [nf-next PATCH v2] netfilter: nft_exthdr: Fix for unsafe packet data read Message-ID: <20210608100754.GG20020@breakpoint.cc> References: <20210608094057.24598-1-phil@nwl.cc> <20210608095621.GA15808@salvia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210608095621.GA15808@salvia> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org 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.