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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1755AC433F5 for ; Mon, 10 Oct 2022 17:44:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229837AbiJJRoz (ORCPT ); Mon, 10 Oct 2022 13:44:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49768 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229796AbiJJRow (ORCPT ); Mon, 10 Oct 2022 13:44:52 -0400 Received: from smtp-fw-33001.amazon.com (smtp-fw-33001.amazon.com [207.171.190.10]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E48C914001; Mon, 10 Oct 2022 10:44:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1665423890; x=1696959890; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=cEYe75lf39NbvHuzf7+Ww4Mv5GZJeDIvvrLUvbELky0=; b=mawTZGayKCZxBAnL/Yun2kI+198CuIZhPzNThJYAQPEJA219x2IbtvQq XHOCrwtAYChkxFMtAcDMkuRmfTOyNuJ/BDF5n7b+YcBdlZ3q15MUekjzJ H8x52OHaUtyb4yCA8G2YmQy+SzRhrq8bxqH4ZEV/5UeJ10epVdFzaJOyz Q=; X-IronPort-AV: E=Sophos;i="5.95,173,1661817600"; d="scan'208";a="232124636" Received: from iad12-co-svc-p1-lb1-vlan3.amazon.com (HELO email-inbound-relay-iad-1e-8be8ed69.us-east-1.amazon.com) ([10.43.8.6]) by smtp-border-fw-33001.sea14.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Oct 2022 17:44:31 +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-8be8ed69.us-east-1.amazon.com (Postfix) with ESMTPS id 5B62FC0822; Mon, 10 Oct 2022 17:44:27 +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; Mon, 10 Oct 2022 17:44:26 +0000 Received: from 88665a182662.ant.amazon.com (10.43.160.124) 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; Mon, 10 Oct 2022 17:44:20 +0000 From: Kuniyuki Iwashima To: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Hideaki YOSHIFUJI , David Ahern , Martin KaFai Lau CC: Craig Gallek , Willem de Bruijn , Kuniyuki Iwashima , Kuniyuki Iwashima , , Subject: [PATCH v1 net 1/3] udp: Update reuse->has_conns under reuseport_lock. Date: Mon, 10 Oct 2022 10:43:49 -0700 Message-ID: <20221010174351.11024-2-kuniyu@amazon.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20221010174351.11024-1-kuniyu@amazon.com> References: <20221010174351.11024-1-kuniyu@amazon.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.43.160.124] X-ClientProxiedBy: EX13D22UWC002.ant.amazon.com (10.43.162.29) To EX19D004ANA001.ant.amazon.com (10.37.240.138) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When we call connect() for a UDP socket in a reuseport group, we have to update sk->sk_reuseport_cb->has_conns to 1. Otherwise, the kernel could select a unconnected socket wrongly for packets sent to the connected socket. However, the current way to set has_conns is illegal and possible to trigger that problem. reuseport_has_conns() changes has_conns under rcu_read_lock(), which upgrades the RCU reader to the updater. Then, it must do the update under the updater's lock, reuseport_lock, but it doesn't for now. For this reason, there is a race below where we fail to set has_conns resulting in the wrong socket selection. To avoid the race, let's split the reader and updater with proper locking. cpu1 cpu2 +----+ +----+ __ip[46]_datagram_connect() reuseport_grow() . . |- reuseport_has_conns(sk, true) |- more_reuse = __reuseport_alloc(more_socks_size) | . | | |- rcu_read_lock() | |- reuse = rcu_dereference(sk->sk_reuseport_cb) | | | | | /* reuse->has_conns == 0 here */ | | |- more_reuse->has_conns = reuse->has_conns | |- reuse->has_conns = 1 | /* more_reuse->has_conns SHOULD BE 1 HERE */ | | | | | |- rcu_assign_pointer(reuse->socks[i]->sk_reuseport_cb, | | | more_reuse) | `- rcu_read_unlock() `- kfree_rcu(reuse, rcu) | |- sk->sk_state = TCP_ESTABLISHED Fixes: acdcecc61285 ("udp: correct reuseport selection with connected sockets") Signed-off-by: Kuniyuki Iwashima --- include/net/sock_reuseport.h | 23 +++++++++++++++++------ net/ipv4/datagram.c | 2 +- net/ipv4/udp.c | 2 +- net/ipv6/datagram.c | 2 +- net/ipv6/udp.c | 2 +- 5 files changed, 21 insertions(+), 10 deletions(-) diff --git a/include/net/sock_reuseport.h b/include/net/sock_reuseport.h index 473b0b0fa4ab..fe9779e6d90f 100644 --- a/include/net/sock_reuseport.h +++ b/include/net/sock_reuseport.h @@ -43,21 +43,32 @@ struct sock *reuseport_migrate_sock(struct sock *sk, extern int reuseport_attach_prog(struct sock *sk, struct bpf_prog *prog); extern int reuseport_detach_prog(struct sock *sk); -static inline bool reuseport_has_conns(struct sock *sk, bool set) +static inline bool reuseport_has_conns(struct sock *sk) { struct sock_reuseport *reuse; bool ret = false; rcu_read_lock(); reuse = rcu_dereference(sk->sk_reuseport_cb); - if (reuse) { - if (set) - reuse->has_conns = 1; - ret = reuse->has_conns; - } + if (reuse && reuse->has_conns) + ret = true; rcu_read_unlock(); return ret; } +static inline void reuseport_has_conns_set(struct sock *sk) +{ + struct sock_reuseport *reuse; + + if (!rcu_access_pointer(sk->sk_reuseport_cb)) + return; + + spin_lock(&reuseport_lock); + reuse = rcu_dereference_protected(sk->sk_reuseport_cb, + lockdep_is_held(&reuseport_lock)); + reuse->has_conns = 1; + spin_unlock(&reuseport_lock); +} + #endif /* _SOCK_REUSEPORT_H */ diff --git a/net/ipv4/datagram.c b/net/ipv4/datagram.c index 405a8c2aea64..5e66add7befa 100644 --- a/net/ipv4/datagram.c +++ b/net/ipv4/datagram.c @@ -70,7 +70,7 @@ int __ip4_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len } inet->inet_daddr = fl4->daddr; inet->inet_dport = usin->sin_port; - reuseport_has_conns(sk, true); + reuseport_has_conns_set(sk); sk->sk_state = TCP_ESTABLISHED; sk_set_txhash(sk); inet->inet_id = prandom_u32(); diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index d63118ce5900..29228231b058 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -448,7 +448,7 @@ static struct sock *udp4_lib_lookup2(struct net *net, result = lookup_reuseport(net, sk, skb, saddr, sport, daddr, hnum); /* Fall back to scoring if group has connections */ - if (result && !reuseport_has_conns(sk, false)) + if (result && !reuseport_has_conns(sk)) return result; result = result ? : sk; diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c index df665d4e8f0f..5ecb56522f9d 100644 --- a/net/ipv6/datagram.c +++ b/net/ipv6/datagram.c @@ -256,7 +256,7 @@ int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr, goto out; } - reuseport_has_conns(sk, true); + reuseport_has_conns_set(sk); sk->sk_state = TCP_ESTABLISHED; sk_set_txhash(sk); out: diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c index 91e795bb9ade..56e4523a3004 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -182,7 +182,7 @@ static struct sock *udp6_lib_lookup2(struct net *net, result = lookup_reuseport(net, sk, skb, saddr, sport, daddr, hnum); /* Fall back to scoring if group has connections */ - if (result && !reuseport_has_conns(sk, false)) + if (result && !reuseport_has_conns(sk)) return result; result = result ? : sk; -- 2.30.2