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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 E6A69C2D0DB for ; Tue, 28 Jan 2020 14:26:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BF31024685 for ; Tue, 28 Jan 2020 14:26:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1580221562; bh=1EACH4F58ZD1tdnCTIw6HDtVwy8XumsZjIIU30TsouU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=ts8JbN2gjRR1/usWdw/CSPSyiImFmku1kKVztBGKYGcYY/ctr40qyv6leaykLuHdT obv3I4Mc8cyfRDJI/Nze6tfj7desAuAEm0dqhe5t1PQvv1Muixl5+mzIIJk2Dho+Cx D0xYlXsnVKVhd8rSN3jKp/dVv/6UewM4wOjiTCU0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733117AbgA1O0C (ORCPT ); Tue, 28 Jan 2020 09:26:02 -0500 Received: from mail.kernel.org ([198.145.29.99]:53158 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729663AbgA1OZ6 (ORCPT ); Tue, 28 Jan 2020 09:25:58 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8355824685; Tue, 28 Jan 2020 14:25:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1580221558; bh=1EACH4F58ZD1tdnCTIw6HDtVwy8XumsZjIIU30TsouU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NNnvQd5ta9WIS6mp9yhO9ac9fyfGpOObt8XY51EgQr4TNufYQmm4wNf/FbZnEdNMB 5xvmKuNzmYXH9KkRAyJ3INpe8Jl6HrbBbHv0MV5cvYt4s6CSLFKYRet/UtJzzNyf3q 4P+7Ie1wBoh5TDivnPjTe8URwstUf5CNzvDIjs/k= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Willem de Bruijn , "David S. Miller" , Sasha Levin Subject: [PATCH 4.9 226/271] packet: fix data-race in fanout_flow_is_huge() Date: Tue, 28 Jan 2020 15:06:15 +0100 Message-Id: <20200128135909.384939014@linuxfoundation.org> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200128135852.449088278@linuxfoundation.org> References: <20200128135852.449088278@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Eric Dumazet [ Upstream commit b756ad928d98e5ef0b74af7546a6a31a8dadde00 ] KCSAN reported the following data-race [1] Adding a couple of READ_ONCE()/WRITE_ONCE() should silence it. Since the report hinted about multiple cpus using the history concurrently, I added a test avoiding writing on it if the victim slot already contains the desired value. [1] BUG: KCSAN: data-race in fanout_demux_rollover / fanout_demux_rollover read to 0xffff8880b01786cc of 4 bytes by task 18921 on cpu 1: fanout_flow_is_huge net/packet/af_packet.c:1303 [inline] fanout_demux_rollover+0x33e/0x3f0 net/packet/af_packet.c:1353 packet_rcv_fanout+0x34e/0x490 net/packet/af_packet.c:1453 deliver_skb net/core/dev.c:1888 [inline] dev_queue_xmit_nit+0x15b/0x540 net/core/dev.c:1958 xmit_one net/core/dev.c:3195 [inline] dev_hard_start_xmit+0x3f5/0x430 net/core/dev.c:3215 __dev_queue_xmit+0x14ab/0x1b40 net/core/dev.c:3792 dev_queue_xmit+0x21/0x30 net/core/dev.c:3825 neigh_direct_output+0x1f/0x30 net/core/neighbour.c:1530 neigh_output include/net/neighbour.h:511 [inline] ip6_finish_output2+0x7a2/0xec0 net/ipv6/ip6_output.c:116 __ip6_finish_output net/ipv6/ip6_output.c:142 [inline] __ip6_finish_output+0x2d7/0x330 net/ipv6/ip6_output.c:127 ip6_finish_output+0x41/0x160 net/ipv6/ip6_output.c:152 NF_HOOK_COND include/linux/netfilter.h:294 [inline] ip6_output+0xf2/0x280 net/ipv6/ip6_output.c:175 dst_output include/net/dst.h:436 [inline] ip6_local_out+0x74/0x90 net/ipv6/output_core.c:179 ip6_send_skb+0x53/0x110 net/ipv6/ip6_output.c:1795 udp_v6_send_skb.isra.0+0x3ec/0xa70 net/ipv6/udp.c:1173 udpv6_sendmsg+0x1906/0x1c20 net/ipv6/udp.c:1471 inet6_sendmsg+0x6d/0x90 net/ipv6/af_inet6.c:576 sock_sendmsg_nosec net/socket.c:637 [inline] sock_sendmsg+0x9f/0xc0 net/socket.c:657 ___sys_sendmsg+0x2b7/0x5d0 net/socket.c:2311 __sys_sendmmsg+0x123/0x350 net/socket.c:2413 __do_sys_sendmmsg net/socket.c:2442 [inline] __se_sys_sendmmsg net/socket.c:2439 [inline] __x64_sys_sendmmsg+0x64/0x80 net/socket.c:2439 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x44/0xa9 write to 0xffff8880b01786cc of 4 bytes by task 18922 on cpu 0: fanout_flow_is_huge net/packet/af_packet.c:1306 [inline] fanout_demux_rollover+0x3a4/0x3f0 net/packet/af_packet.c:1353 packet_rcv_fanout+0x34e/0x490 net/packet/af_packet.c:1453 deliver_skb net/core/dev.c:1888 [inline] dev_queue_xmit_nit+0x15b/0x540 net/core/dev.c:1958 xmit_one net/core/dev.c:3195 [inline] dev_hard_start_xmit+0x3f5/0x430 net/core/dev.c:3215 __dev_queue_xmit+0x14ab/0x1b40 net/core/dev.c:3792 dev_queue_xmit+0x21/0x30 net/core/dev.c:3825 neigh_direct_output+0x1f/0x30 net/core/neighbour.c:1530 neigh_output include/net/neighbour.h:511 [inline] ip6_finish_output2+0x7a2/0xec0 net/ipv6/ip6_output.c:116 __ip6_finish_output net/ipv6/ip6_output.c:142 [inline] __ip6_finish_output+0x2d7/0x330 net/ipv6/ip6_output.c:127 ip6_finish_output+0x41/0x160 net/ipv6/ip6_output.c:152 NF_HOOK_COND include/linux/netfilter.h:294 [inline] ip6_output+0xf2/0x280 net/ipv6/ip6_output.c:175 dst_output include/net/dst.h:436 [inline] ip6_local_out+0x74/0x90 net/ipv6/output_core.c:179 ip6_send_skb+0x53/0x110 net/ipv6/ip6_output.c:1795 udp_v6_send_skb.isra.0+0x3ec/0xa70 net/ipv6/udp.c:1173 udpv6_sendmsg+0x1906/0x1c20 net/ipv6/udp.c:1471 inet6_sendmsg+0x6d/0x90 net/ipv6/af_inet6.c:576 sock_sendmsg_nosec net/socket.c:637 [inline] sock_sendmsg+0x9f/0xc0 net/socket.c:657 ___sys_sendmsg+0x2b7/0x5d0 net/socket.c:2311 __sys_sendmmsg+0x123/0x350 net/socket.c:2413 __do_sys_sendmmsg net/socket.c:2442 [inline] __se_sys_sendmmsg net/socket.c:2439 [inline] __x64_sys_sendmmsg+0x64/0x80 net/socket.c:2439 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Reported by Kernel Concurrency Sanitizer on: CPU: 0 PID: 18922 Comm: syz-executor.3 Not tainted 5.4.0-rc6+ #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Fixes: 3b3a5b0aab5b ("packet: rollover huge flows before small flows") Signed-off-by: Eric Dumazet Cc: Willem de Bruijn Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/packet/af_packet.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 47a862cc7b349..fb643945e4244 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1332,15 +1332,21 @@ static void packet_sock_destruct(struct sock *sk) static bool fanout_flow_is_huge(struct packet_sock *po, struct sk_buff *skb) { - u32 rxhash; + u32 *history = po->rollover->history; + u32 victim, rxhash; int i, count = 0; rxhash = skb_get_hash(skb); for (i = 0; i < ROLLOVER_HLEN; i++) - if (po->rollover->history[i] == rxhash) + if (READ_ONCE(history[i]) == rxhash) count++; - po->rollover->history[prandom_u32() % ROLLOVER_HLEN] = rxhash; + victim = prandom_u32() % ROLLOVER_HLEN; + + /* Avoid dirtying the cache line if possible */ + if (READ_ONCE(history[victim]) != rxhash) + WRITE_ONCE(history[victim], rxhash); + return count > (ROLLOVER_HLEN >> 1); } -- 2.20.1