From patchwork Mon Mar 30 19:21:35 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Pablo Neira Ayuso X-Patchwork-Id: 221568 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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT 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 8788AC43331 for ; Mon, 30 Mar 2020 19:22:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6DE332072E for ; Mon, 30 Mar 2020 19:22:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728916AbgC3TWa (ORCPT ); Mon, 30 Mar 2020 15:22:30 -0400 Received: from correo.us.es ([193.147.175.20]:48524 "EHLO mail.us.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728391AbgC3TWF (ORCPT ); Mon, 30 Mar 2020 15:22:05 -0400 Received: from antivirus1-rhel7.int (unknown [192.168.2.11]) by mail.us.es (Postfix) with ESMTP id 1B189B4989 for ; Mon, 30 Mar 2020 21:21:57 +0200 (CEST) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id 03DE8FF6F5 for ; Mon, 30 Mar 2020 21:21:57 +0200 (CEST) Received: by antivirus1-rhel7.int (Postfix, from userid 99) id BA572123979; Mon, 30 Mar 2020 21:21:51 +0200 (CEST) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id A5741100A69; Mon, 30 Mar 2020 21:21:48 +0200 (CEST) Received: from 192.168.1.97 (192.168.1.97) by antivirus1-rhel7.int (F-Secure/fsigk_smtp/550/antivirus1-rhel7.int); Mon, 30 Mar 2020 21:21:48 +0200 (CEST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/antivirus1-rhel7.int) Received: from salvia.here (unknown [90.77.255.23]) (Authenticated sender: pneira@us.es) by entrada.int (Postfix) with ESMTPA id 7C13442EF4E1; Mon, 30 Mar 2020 21:21:48 +0200 (CEST) X-SMTPAUTHUS: auth mail.us.es From: Pablo Neira Ayuso To: netfilter-devel@vger.kernel.org Cc: davem@davemloft.net, netdev@vger.kernel.org Subject: [PATCH 27/28] netfilter: nft_exthdr: fix endianness of tcp option cast Date: Mon, 30 Mar 2020 21:21:35 +0200 Message-Id: <20200330192136.230459-28-pablo@netfilter.org> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20200330192136.230459-1-pablo@netfilter.org> References: <20200330192136.230459-1-pablo@netfilter.org> MIME-Version: 1.0 X-Virus-Scanned: ClamAV using ClamSMTP Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Sergey Marinkevich I got a problem on MIPS with Big-Endian is turned on: every time when NF trying to change TCP MSS it returns because of new.v16 was greater than old.v16. But real MSS was 1460 and my rule was like this: add rule table chain tcp option maxseg size set 1400 And 1400 is lesser that 1460, not greater. Later I founded that main causer is cast from u32 to __be16. Debugging: In example MSS = 1400(HEX: 0x578). Here is representation of each byte like it is in memory by addresses from left to right(e.g. [0x0 0x1 0x2 0x3]). LE — Little-Endian system, BE — Big-Endian, left column is type. LE BE u32: [78 05 00 00] [00 00 05 78] As you can see, u32 representation will be casted to u16 from different half of 4-byte address range. But actually nf_tables uses registers and store data of various size. Actually TCP MSS stored in 2 bytes. But registers are still u32 in definition: struct nft_regs { union { u32 data[20]; struct nft_verdict verdict; }; }; So, access like regs->data[priv->sreg] exactly u32. So, according to table presents above, per-byte representation of stored TCP MSS in register will be: LE BE (u32)regs->data[]: [78 05 00 00] [05 78 00 00] ^^ ^^ We see that register uses just half of u32 and other 2 bytes may be used for some another data. But in nft_exthdr_tcp_set_eval() it casted just like u32 -> __be16: new.v16 = src But u32 overfill __be16, so it get 2 low bytes. For clarity draw one more table( means that bytes will be used for cast). LE BE u32: [<78 05> 00 00] [00 00 <05 78>] (u32)regs->data[]: [<78 05> 00 00] [05 78 <00 00>] As you can see, for Little-Endian nothing changes, but for Big-endian we take the wrong half. In my case there is some other data instead of zeros, so new MSS was wrongly greater. For shooting this bug I used solution for ports ranges. Applying of this patch does not affect Little-Endian systems. Signed-off-by: Sergey Marinkevich Acked-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nft_exthdr.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/net/netfilter/nft_exthdr.c b/net/netfilter/nft_exthdr.c index a5e8469859e3..07782836fad6 100644 --- a/net/netfilter/nft_exthdr.c +++ b/net/netfilter/nft_exthdr.c @@ -228,7 +228,6 @@ static void nft_exthdr_tcp_set_eval(const struct nft_expr *expr, unsigned int i, optl, tcphdr_len, offset; struct tcphdr *tcph; u8 *opt; - u32 src; tcph = nft_tcp_header_pointer(pkt, sizeof(buff), buff, &tcphdr_len); if (!tcph) @@ -237,7 +236,6 @@ static void nft_exthdr_tcp_set_eval(const struct nft_expr *expr, opt = (u8 *)tcph; for (i = sizeof(*tcph); i < tcphdr_len - 1; i += optl) { union { - u8 octet; __be16 v16; __be32 v32; } old, new; @@ -259,13 +257,13 @@ static void nft_exthdr_tcp_set_eval(const struct nft_expr *expr, if (!tcph) return; - src = regs->data[priv->sreg]; offset = i + priv->offset; switch (priv->len) { case 2: old.v16 = get_unaligned((u16 *)(opt + offset)); - new.v16 = src; + new.v16 = (__force __be16)nft_reg_load16( + ®s->data[priv->sreg]); switch (priv->type) { case TCPOPT_MSS: @@ -283,7 +281,7 @@ static void nft_exthdr_tcp_set_eval(const struct nft_expr *expr, old.v16, new.v16, false); break; case 4: - new.v32 = src; + new.v32 = regs->data[priv->sreg]; old.v32 = get_unaligned((u32 *)(opt + offset)); if (old.v32 == new.v32)