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=-19.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 017AAC432BE for ; Mon, 26 Jul 2021 16:14:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DFD6560F94 for ; Mon, 26 Jul 2021 16:14:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234809AbhGZPd6 (ORCPT ); Mon, 26 Jul 2021 11:33:58 -0400 Received: from mail.kernel.org ([198.145.29.99]:47948 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233853AbhGZPcp (ORCPT ); Mon, 26 Jul 2021 11:32:45 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id E7BD36056B; Mon, 26 Jul 2021 16:13:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1627315993; bh=6UZPrlVew1vjSX2qIq1Eea5jnQsUb/Gvdqafg42Ky5k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ja0iGPY2CqoE4FOoAQoFCJnG7urJ3Yo6QucxId6S9PYHcAr8AS5VwaaT3HA0Rv9qd k6xAOZVCrOOWc3xnOxB6nbKmDSML5lPdR6de+0phOyaa0YSLx97/xEyzsOSjOam/BR KCOclDSy8jIr0654rD5qhDpsbn1JxgyXFhQ7GweE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Wei Wang , Yuchung Cheng , Neal Cardwell , "David S. Miller" , Sasha Levin Subject: [PATCH 5.13 111/223] net/tcp_fastopen: fix data races around tfo_active_disable_stamp Date: Mon, 26 Jul 2021 17:38:23 +0200 Message-Id: <20210726153849.906205897@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210726153846.245305071@linuxfoundation.org> References: <20210726153846.245305071@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Eric Dumazet [ Upstream commit 6f20c8adb1813467ea52c1296d52c4e95978cb2f ] tfo_active_disable_stamp is read and written locklessly. We need to annotate these accesses appropriately. Then, we need to perform the atomic_inc(tfo_active_disable_times) after the timestamp has been updated, and thus add barriers to make sure tcp_fastopen_active_should_disable() wont read a stale timestamp. Fixes: cf1ef3f0719b ("net/tcp_fastopen: Disable active side TFO in certain scenarios") Signed-off-by: Eric Dumazet Cc: Wei Wang Cc: Yuchung Cheng Cc: Neal Cardwell Acked-by: Wei Wang Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/ipv4/tcp_fastopen.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c index af2814c9342a..08548ff23d83 100644 --- a/net/ipv4/tcp_fastopen.c +++ b/net/ipv4/tcp_fastopen.c @@ -507,8 +507,15 @@ void tcp_fastopen_active_disable(struct sock *sk) { struct net *net = sock_net(sk); + /* Paired with READ_ONCE() in tcp_fastopen_active_should_disable() */ + WRITE_ONCE(net->ipv4.tfo_active_disable_stamp, jiffies); + + /* Paired with smp_rmb() in tcp_fastopen_active_should_disable(). + * We want net->ipv4.tfo_active_disable_stamp to be updated first. + */ + smp_mb__before_atomic(); atomic_inc(&net->ipv4.tfo_active_disable_times); - net->ipv4.tfo_active_disable_stamp = jiffies; + NET_INC_STATS(net, LINUX_MIB_TCPFASTOPENBLACKHOLE); } @@ -526,10 +533,16 @@ bool tcp_fastopen_active_should_disable(struct sock *sk) if (!tfo_da_times) return false; + /* Paired with smp_mb__before_atomic() in tcp_fastopen_active_disable() */ + smp_rmb(); + /* Limit timout to max: 2^6 * initial timeout */ multiplier = 1 << min(tfo_da_times - 1, 6); - timeout = multiplier * tfo_bh_timeout * HZ; - if (time_before(jiffies, sock_net(sk)->ipv4.tfo_active_disable_stamp + timeout)) + + /* Paired with the WRITE_ONCE() in tcp_fastopen_active_disable(). */ + timeout = READ_ONCE(sock_net(sk)->ipv4.tfo_active_disable_stamp) + + multiplier * tfo_bh_timeout * HZ; + if (time_before(jiffies, timeout)) return true; /* Mark check bit so we can check for successful active TFO -- 2.30.2