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=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, 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 8682EC2D0DB for ; Wed, 29 Jan 2020 14:55:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6079E2070E for ; Wed, 29 Jan 2020 14:55:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726750AbgA2OzO (ORCPT ); Wed, 29 Jan 2020 09:55:14 -0500 Received: from Chamillionaire.breakpoint.cc ([193.142.43.52]:42584 "EHLO Chamillionaire.breakpoint.cc" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726721AbgA2OzN (ORCPT ); Wed, 29 Jan 2020 09:55:13 -0500 Received: from fw by Chamillionaire.breakpoint.cc with local (Exim 4.92) (envelope-from ) id 1iwokJ-00078n-Gd; Wed, 29 Jan 2020 15:55:11 +0100 From: Florian Westphal To: Cc: matthieu.baerts@tessares.net, mathew.j.martineau@linux.intel.com, Florian Westphal , Eric Dumazet , Christoph Paasch Subject: [PATCH net 4/4] mptcp: handle tcp fallback when using syn cookies Date: Wed, 29 Jan 2020 15:54:46 +0100 Message-Id: <20200129145446.26425-5-fw@strlen.de> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200129145446.26425-1-fw@strlen.de> References: <20200129145446.26425-1-fw@strlen.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org We can't deal with syncookie mode yet, the syncookie rx path will create tcp reqsk, i.e. we get OOB access because we treat tcp reqsk as mptcp reqsk one: TCP: SYN flooding on port 20002. Sending cookies. BUG: KASAN: slab-out-of-bounds in subflow_syn_recv_sock+0x451/0x4d0 net/mptcp/subflow.c:191 Read of size 1 at addr ffff8881167bc148 by task syz-executor099/2120 subflow_syn_recv_sock+0x451/0x4d0 net/mptcp/subflow.c:191 tcp_get_cookie_sock+0xcf/0x520 net/ipv4/syncookies.c:209 cookie_v6_check+0x15a5/0x1e90 net/ipv6/syncookies.c:252 tcp_v6_cookie_check net/ipv6/tcp_ipv6.c:1123 [inline] [..] Bug can be reproduced via "sysctl net.ipv4.tcp_syncookies=2". Note that MPTCP should work with syncookies (4th ack would carry needed state), but it appears better to sort that out in -next so do tcp fallback for now. I removed the MPTCP ifdef for tcp_rsk "is_mptcp" member because if (IS_ENABLED()) is easier to read than "#ifdef IS_ENABLED()/#endif" pair. Cc: Eric Dumazet Fixes: cec37a6e41aae7bf ("mptcp: Handle MP_CAPABLE options for outgoing connections") Reported-by: Christoph Paasch Tested-by: Christoph Paasch Signed-off-by: Florian Westphal --- include/linux/tcp.h | 2 -- net/ipv4/syncookies.c | 4 ++++ net/ipv4/tcp_input.c | 3 +++ net/ipv6/syncookies.c | 3 +++ net/mptcp/subflow.c | 5 ++++- 5 files changed, 14 insertions(+), 3 deletions(-) diff --git a/include/linux/tcp.h b/include/linux/tcp.h index 1cf73e6f85ca..3dc964010fef 100644 --- a/include/linux/tcp.h +++ b/include/linux/tcp.h @@ -148,9 +148,7 @@ struct tcp_request_sock { const struct tcp_request_sock_ops *af_specific; u64 snt_synack; /* first SYNACK sent time */ bool tfo_listener; -#if IS_ENABLED(CONFIG_MPTCP) bool is_mptcp; -#endif u32 txhash; u32 rcv_isn; u32 snt_isn; diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c index 345b2b0ff618..9a4f6b16c9bc 100644 --- a/net/ipv4/syncookies.c +++ b/net/ipv4/syncookies.c @@ -349,6 +349,10 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb) req->ts_recent = tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0; treq->snt_synack = 0; treq->tfo_listener = false; + + if (IS_ENABLED(CONFIG_MPTCP)) + treq->is_mptcp = 0; + if (IS_ENABLED(CONFIG_SMC)) ireq->smc_ok = 0; diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index e8b840a4767e..e325b4506e25 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -6637,6 +6637,9 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops, af_ops->init_req(req, sk, skb); + if (IS_ENABLED(CONFIG_MPTCP) && want_cookie) + tcp_rsk(req)->is_mptcp = 0; + if (security_inet_conn_request(sk, skb, req)) goto drop_and_free; diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c index 30915f6f31e3..13235a012388 100644 --- a/net/ipv6/syncookies.c +++ b/net/ipv6/syncookies.c @@ -178,6 +178,9 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb) treq = tcp_rsk(req); treq->tfo_listener = false; + if (IS_ENABLED(CONFIG_MPTCP)) + treq->is_mptcp = 0; + if (security_inet_conn_request(sk, skb, req)) goto out_free; diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index 205dca1c30b7..c90c0e6ffb82 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -186,6 +186,9 @@ static struct sock *subflow_syn_recv_sock(const struct sock *sk, pr_debug("listener=%p, req=%p, conn=%p", listener, req, listener->conn); + if (tcp_rsk(req)->is_mptcp == 0) + goto create_child; + /* if the sk is MP_CAPABLE, we try to fetch the client key */ subflow_req = mptcp_subflow_rsk(req); if (subflow_req->mp_capable) { @@ -769,7 +772,7 @@ static void subflow_ulp_clone(const struct request_sock *req, struct mptcp_subflow_context *old_ctx = mptcp_subflow_ctx(newsk); struct mptcp_subflow_context *new_ctx; - if (!subflow_req->mp_capable) { + if (!tcp_rsk(req)->is_mptcp || !subflow_req->mp_capable) { subflow_ulp_fallback(newsk, old_ctx); return; } -- 2.24.1