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=-3.7 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 012F0C35242 for ; Sat, 8 Feb 2020 18:31:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D7701217BA for ; Sat, 8 Feb 2020 18:31:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728332AbgBHSbd (ORCPT ); Sat, 8 Feb 2020 13:31:33 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:34784 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727969AbgBHS3u (ORCPT ); Sat, 8 Feb 2020 13:29:50 -0500 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 1j0UrO-0003iN-K9; Sat, 08 Feb 2020 18:29:42 +0000 Received: from ben by deadeye with local (Exim 4.93) (envelope-from ) id 1j0UrN-000CX7-08; Sat, 08 Feb 2020 18:29:41 +0000 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 , "David S. Miller" , "Florian Westphal" , "Eric Dumazet" , "Yuchung Cheng" Date: Sat, 08 Feb 2020 18:21:20 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 141/148] tcp: syncookies: extend validity range 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 3.16.82-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet commit 264ea103a7473f51aced838e68ed384ea2c759f5 upstream. Now we allow storing more request socks per listener, we might hit syncookie mode less often and hit following bug in our stack : When we send a burst of syncookies, then exit this mode, tcp_synq_no_recent_overflow() can return false if the ACK packets coming from clients are coming three seconds after the end of syncookie episode. This is a way too strong requirement and conflicts with rest of syncookie code which allows ACK to be aged up to 2 minutes. Perfectly valid ACK packets are dropped just because clients might be in a crowded wifi environment or on another planet. So let's fix this, and also change tcp_synq_overflow() to not dirty a cache line for every syncookie we send, as we are under attack. Signed-off-by: Eric Dumazet Acked-by: Florian Westphal Acked-by: Yuchung Cheng Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings --- include/net/tcp.h | 38 ++++++++++++++++++++++++-------------- 1 file changed, 24 insertions(+), 14 deletions(-) --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -326,18 +326,6 @@ static inline bool tcp_too_many_orphans( bool tcp_check_oom(struct sock *sk, int shift); -/* syncookies: remember time of last synqueue overflow */ -static inline void tcp_synq_overflow(struct sock *sk) -{ - tcp_sk(sk)->rx_opt.ts_recent_stamp = jiffies; -} - -/* syncookies: no recent synqueue overflow on this listening socket? */ -static inline bool tcp_synq_no_recent_overflow(const struct sock *sk) -{ - unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp; - return time_after(jiffies, last_overflow + TCP_TIMEOUT_FALLBACK); -} extern struct proto tcp_prot; @@ -485,13 +473,35 @@ struct sock *cookie_v4_check(struct sock * i.e. a sent cookie is valid only at most for 2*60 seconds (or less if * the counter advances immediately after a cookie is generated). */ -#define MAX_SYNCOOKIE_AGE 2 +#define MAX_SYNCOOKIE_AGE 2 +#define TCP_SYNCOOKIE_PERIOD (60 * HZ) +#define TCP_SYNCOOKIE_VALID (MAX_SYNCOOKIE_AGE * TCP_SYNCOOKIE_PERIOD) + +/* syncookies: remember time of last synqueue overflow + * But do not dirty this field too often (once per second is enough) + */ +static inline void tcp_synq_overflow(struct sock *sk) +{ + unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp; + unsigned long now = jiffies; + + if (time_after(now, last_overflow + HZ)) + tcp_sk(sk)->rx_opt.ts_recent_stamp = now; +} + +/* syncookies: no recent synqueue overflow on this listening socket? */ +static inline bool tcp_synq_no_recent_overflow(const struct sock *sk) +{ + unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp; + + return time_after(jiffies, last_overflow + TCP_SYNCOOKIE_VALID); +} static inline u32 tcp_cookie_time(void) { u64 val = get_jiffies_64(); - do_div(val, 60 * HZ); + do_div(val, TCP_SYNCOOKIE_PERIOD); return val; }