From nobody Mon Apr 6 19:37:49 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0A4A8C433F5 for ; Tue, 4 Oct 2022 17:41:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229940AbiJDRlO (ORCPT ); Tue, 4 Oct 2022 13:41:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41398 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229962AbiJDRkt (ORCPT ); Tue, 4 Oct 2022 13:40:49 -0400 Received: from smtp-fw-80006.amazon.com (smtp-fw-80006.amazon.com [99.78.197.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BE2E313CCB; Tue, 4 Oct 2022 10:40:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1664905244; x=1696441244; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=rbvL8Z4wQdanPlBmtqdlCOVfEgaVrfU/1/xOOxjyWmU=; b=kPOLBuRvGmWoCd+titsjX7ufrhQ7N6zUaoZUGe5x6BBwR3KIfLf7LLyi 4zIikPdg/fwrnVse0hIcvc+d3ui1ZvNPIdOf5mAABs+qUkazj26mEhiBJ TWqDAU9tJHd3aiQ9Iveww9bzs10aw4GWwusIjHtOJSc1jFmpHmXibNnC7 A=; X-IronPort-AV: E=Sophos;i="5.95,158,1661817600"; d="scan'208";a="136783143" Received: from pdx4-co-svc-p1-lb2-vlan2.amazon.com (HELO email-inbound-relay-iad-1e-fc41acad.us-east-1.amazon.com) ([10.25.36.210]) by smtp-border-fw-80006.pdx80.corp.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Oct 2022 17:19:45 +0000 Received: from EX13MTAUWB001.ant.amazon.com (iad12-ws-svc-p26-lb9-vlan3.iad.amazon.com [10.40.163.38]) by email-inbound-relay-iad-1e-fc41acad.us-east-1.amazon.com (Postfix) with ESMTPS id F1F96C41B7; Tue, 4 Oct 2022 17:19:41 +0000 (UTC) Received: from EX19D004ANA001.ant.amazon.com (10.37.240.138) by EX13MTAUWB001.ant.amazon.com (10.43.161.249) with Microsoft SMTP Server (TLS) id 15.0.1497.38; Tue, 4 Oct 2022 17:19:40 +0000 Received: from 88665a182662.ant.amazon.com (10.43.161.176) by EX19D004ANA001.ant.amazon.com (10.37.240.138) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1118.12; Tue, 4 Oct 2022 17:19:33 +0000 From: Kuniyuki Iwashima To: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , David Ahern , Hideaki YOSHIFUJI CC: Kuniyuki Iwashima , Kuniyuki Iwashima , , , , syzbot Subject: [PATCH v4 net 5/5] tcp: Fix data races around icsk->icsk_af_ops. Date: Tue, 4 Oct 2022 10:18:02 -0700 Message-ID: <20221004171802.40968-6-kuniyu@amazon.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20221004171802.40968-1-kuniyu@amazon.com> References: <20221004171802.40968-1-kuniyu@amazon.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.43.161.176] X-ClientProxiedBy: EX13D49UWC003.ant.amazon.com (10.43.162.10) To EX19D004ANA001.ant.amazon.com (10.37.240.138) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" setsockopt(IPV6_ADDRFORM) and tcp_v6_connect() change icsk->icsk_af_ops under lock_sock(), but tcp_(get|set)sockopt() read it locklessly. To avoid load/store tearing, we need to add READ_ONCE() and WRITE_ONCE() for the reads and writes. Thanks to Eric Dumazet for providing the syzbot report: BUG: KCSAN: data-race in tcp_setsockopt / tcp_v6_connect write to 0xffff88813c624518 of 8 bytes by task 23936 on cpu 0: tcp_v6_connect+0x5b3/0xce0 net/ipv6/tcp_ipv6.c:240 __inet_stream_connect+0x159/0x6d0 net/ipv4/af_inet.c:660 inet_stream_connect+0x44/0x70 net/ipv4/af_inet.c:724 __sys_connect_file net/socket.c:1976 [inline] __sys_connect+0x197/0x1b0 net/socket.c:1993 __do_sys_connect net/socket.c:2003 [inline] __se_sys_connect net/socket.c:2000 [inline] __x64_sys_connect+0x3d/0x50 net/socket.c:2000 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd read to 0xffff88813c624518 of 8 bytes by task 23937 on cpu 1: tcp_setsockopt+0x147/0x1c80 net/ipv4/tcp.c:3789 sock_common_setsockopt+0x5d/0x70 net/core/sock.c:3585 __sys_setsockopt+0x212/0x2b0 net/socket.c:2252 __do_sys_setsockopt net/socket.c:2263 [inline] __se_sys_setsockopt net/socket.c:2260 [inline] __x64_sys_setsockopt+0x62/0x70 net/socket.c:2260 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd value changed: 0xffffffff8539af68 -> 0xffffffff8539aff8 Reported by Kernel Concurrency Sanitizer on: CPU: 1 PID: 23937 Comm: syz-executor.5 Not tainted 6.0.0-rc4-syzkaller-00331-g4ed9c1e971b1-dirty #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2022 Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: syzbot Reported-by: Eric Dumazet Signed-off-by: Kuniyuki Iwashima --- net/ipv4/tcp.c | 10 ++++++---- net/ipv6/ipv6_sockglue.c | 3 ++- net/ipv6/tcp_ipv6.c | 6 ++++-- 3 files changed, 12 insertions(+), 7 deletions(-) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 997a80ce1e13..08db82c05a4a 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -3797,8 +3797,9 @@ int tcp_setsockopt(struct sock *sk, int level, int op= tname, sockptr_t optval, const struct inet_connection_sock *icsk =3D inet_csk(sk); =20 if (level !=3D SOL_TCP) - return icsk->icsk_af_ops->setsockopt(sk, level, optname, - optval, optlen); + /* Paired with WRITE_ONCE() in do_ipv6_setsockopt() and tcp_v6_connect()= */ + return READ_ONCE(icsk->icsk_af_ops)->setsockopt(sk, level, optname, + optval, optlen); return do_tcp_setsockopt(sk, level, optname, optval, optlen); } EXPORT_SYMBOL(tcp_setsockopt); @@ -4396,8 +4397,9 @@ int tcp_getsockopt(struct sock *sk, int level, int op= tname, char __user *optval, struct inet_connection_sock *icsk =3D inet_csk(sk); =20 if (level !=3D SOL_TCP) - return icsk->icsk_af_ops->getsockopt(sk, level, optname, - optval, optlen); + /* Paired with WRITE_ONCE() in do_ipv6_setsockopt() and tcp_v6_connect()= */ + return READ_ONCE(icsk->icsk_af_ops)->getsockopt(sk, level, optname, + optval, optlen); return do_tcp_getsockopt(sk, level, optname, optval, optlen); } EXPORT_SYMBOL(tcp_getsockopt); diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c index 2fb9ee413c53..19ac75c2cd54 100644 --- a/net/ipv6/ipv6_sockglue.c +++ b/net/ipv6/ipv6_sockglue.c @@ -479,7 +479,8 @@ static int do_ipv6_setsockopt(struct sock *sk, int leve= l, int optname, =20 /* Paired with READ_ONCE(sk->sk_prot) in inet6_stream_ops */ WRITE_ONCE(sk->sk_prot, &tcp_prot); - icsk->icsk_af_ops =3D &ipv4_specific; + /* Paired with READ_ONCE() in tcp_(get|set)sockopt() */ + WRITE_ONCE(icsk->icsk_af_ops, &ipv4_specific); sk->sk_socket->ops =3D &inet_stream_ops; sk->sk_family =3D PF_INET; tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index e54eee80ce5f..8680aa83f0b9 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -237,7 +237,8 @@ static int tcp_v6_connect(struct sock *sk, struct socka= ddr *uaddr, sin.sin_port =3D usin->sin6_port; sin.sin_addr.s_addr =3D usin->sin6_addr.s6_addr32[3]; =20 - icsk->icsk_af_ops =3D &ipv6_mapped; + /* Paired with READ_ONCE() in tcp_(get|set)sockopt() */ + WRITE_ONCE(icsk->icsk_af_ops, &ipv6_mapped); if (sk_is_mptcp(sk)) mptcpv6_handle_mapped(sk, true); sk->sk_backlog_rcv =3D tcp_v4_do_rcv; @@ -249,7 +250,8 @@ static int tcp_v6_connect(struct sock *sk, struct socka= ddr *uaddr, =20 if (err) { icsk->icsk_ext_hdr_len =3D exthdrlen; - icsk->icsk_af_ops =3D &ipv6_specific; + /* Paired with READ_ONCE() in tcp_(get|set)sockopt() */ + WRITE_ONCE(icsk->icsk_af_ops, &ipv6_specific); if (sk_is_mptcp(sk)) mptcpv6_handle_mapped(sk, false); sk->sk_backlog_rcv =3D tcp_v6_do_rcv; --=20 2.30.2