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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 4E3F7C54FCB for ; Thu, 23 Apr 2020 23:16:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 28F262077D for ; Thu, 23 Apr 2020 23:16:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729617AbgDWXQP (ORCPT ); Thu, 23 Apr 2020 19:16:15 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:49572 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728390AbgDWXGq (ORCPT ); Thu, 23 Apr 2020 19:06:46 -0400 Received: from [192.168.4.242] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1jRkvS-0004hY-Ra; Fri, 24 Apr 2020 00:06:35 +0100 Received: from ben by deadeye with local (Exim 4.93) (envelope-from ) id 1jRkvS-00E6rA-DH; Fri, 24 Apr 2020 00:06:34 +0100 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, Denis Kirjanov , "Pengcheng Yang" , "Eric Dumazet" , "David S. Miller" Date: Fri, 24 Apr 2020 00:06:18 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 151/245] tcp: fix "old stuff" D-SACK causing SACK to be treated as D-SACK In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.242 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.83-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Pengcheng Yang commit c9655008e7845bcfdaac10a1ed8554ec167aea88 upstream. When we receive a D-SACK, where the sequence number satisfies: undo_marker <= start_seq < end_seq <= prior_snd_una we consider this is a valid D-SACK and tcp_is_sackblock_valid() returns true, then this D-SACK is discarded as "old stuff", but the variable first_sack_index is not marked as negative in tcp_sacktag_write_queue(). If this D-SACK also carries a SACK that needs to be processed (for example, the previous SACK segment was lost), this SACK will be treated as a D-SACK in the following processing of tcp_sacktag_write_queue(), which will eventually lead to incorrect updates of undo_retrans and reordering. Fixes: fd6dad616d4f ("[TCP]: Earlier SACK block verification & simplify access to them") Signed-off-by: Pengcheng Yang Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings --- net/ipv4/tcp_input.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -1713,8 +1713,11 @@ tcp_sacktag_write_queue(struct sock *sk, } /* Ignore very old stuff early */ - if (!after(sp[used_sacks].end_seq, prior_snd_una)) + if (!after(sp[used_sacks].end_seq, prior_snd_una)) { + if (i == 0) + first_sack_index = -1; continue; + } used_sacks++; }