From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CE2C844CF52 for ; Mon, 12 Oct 2026 10:10:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791799855; cv=none; b=BVF3uurN867k75MXLX1tJXncjjbGxr4ECPgZP0GgNK4qiNnv8vKZI9b7dvioS5hGjrTuAP/vLu2KdniEbzTHVn1PAIMKJIITqNgRSEIkDoruaQCszGwXPuaDyiPk7O4HPXm+BdEC8XN5QY4BwhXrctOKtbqWH/bNnVnWhzBJE2g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791799855; c=relaxed/simple; bh=xECSW4d1vLvpuH2hQQ0xP+B+zasHTAiB77HZkYJpzgA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Lxqm7YGrQ75vxw4j1WPF7QCeq0fbdvIns9HNpu2SJ29HqWh/7J9AGGmoPgcoV1+EiJVZxXaDDsWYVMMDTDBikovpy78QPqAW6/dRVNNhnWN6BZzlNxGa2KdbbSqkJ3td+K11+/bMbxBJoksfqIkIQ7v71y6Wgmin0O5jIzndz1Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kKyi0ZFM; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="kKyi0ZFM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D7F8F1F0089B; Mon, 12 Oct 2026 10:10:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791799847; bh=7SaiIrHpO4xHOePMxxkGpn90obrjAosd3s3sZ3YJ5EA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=kKyi0ZFMEUhZRFL88Y1BTkY9KsaiQoxP2IF/r5IJyl7Jno3YgPhgsVWOb0CHm8SXb BMAEUEQ6Tt6xOfmCVSa5ELnUeSv+CVgmMBjKgi1p2jUemT/bct1WHi7gYU2wgGg7pj Zdl4YVH8e7+dhxAY32mHnnuTeHIgbKR4CagoJxq3sg7oSAEFesK1AIVlGRTwT2RURq 969XjATeSp5kh1ugRlCjg64sePBGygkKB6GZzcbB86F/9YOLsr+L2vUiCo/UQB1vEW QY8BdCXXCUE3MRaDAdVEWs0ZeLp/mbToW65sNh2SLSCp29vUiK1R9PXXS5feIEtNwM o++7lbN5MAB4Q== From: Eric Dumazet To: "David S . Miller" , Jakub Kicinski , Paolo Abeni Cc: Kuniyuki Iwashima , Neal Cardwell , Ido Schimmel , Theodor Arsenij Larionov Trichkine , Simon Horman , netdev@vger.kernel.org, Eric Dumazet Subject: [PATCH v3 net 2/2] tcp: use the echoed source route in cookie_v4_check() Date: Mon, 12 Oct 2026 12:10:29 +0200 Message-ID: <20261012101029.927296-3-edumazet@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261012101029.927296-1-edumazet@kernel.org> References: <20261012101029.927296-1-edumazet@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit When the ACK carries a source route option, cookie_v4_check() routes the new socket to opt->faddr, where opt points to the options of the received packet. ip_options_compile() only fills faddr for options given by setsockopt() (when called without an skb), so on receive faddr is 0 and the lookup is done for daddr 0, which gives a local route. Use the options echoed by tcp_v4_save_options() instead, as inet_csk_route_req() and inet_csk_route_child_sock() do with ireq->ireq_opt. Read them after security_inet_conn_request(), since CIPSO can replace ireq->ireq_opt there. The route now goes to the first hop of the source route, so also refuse a strict source route through a gateway, as inet_csk_route_req() does. Found by sashiko while reviewing the sk_mc_loop() fix. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Eric Dumazet --- v3: new patch. net/ipv4/syncookies.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c index 73e12976818473277e83ab47f271a43991217e3e..8c9691569e01af0140b8db8990ceeddc3c5fd8fb 100644 --- a/net/ipv4/syncookies.c +++ b/net/ipv4/syncookies.c @@ -404,12 +404,12 @@ static struct request_sock *cookie_tcp_check(struct net *net, struct sock *sk, */ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb) { - struct ip_options *opt = &TCP_SKB_CB(skb)->header.h4.opt; const struct tcphdr *th = tcp_hdr(skb); struct tcp_sock *tp = tcp_sk(sk); struct inet_request_sock *ireq; struct net *net = sock_net(sk); struct tcp_request_sock *treq; + struct ip_options_rcu *opt; struct request_sock *req; struct sock *ret = sk; struct flowi4 fl4; @@ -449,6 +449,8 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb) SKB_DR_SET(reason, SECURITY_HOOK); goto out_free; } + /* Load ireq->ireq_opt after the LSM hook, which can replace it. */ + opt = rcu_dereference_protected(ireq->ireq_opt, true); tcp_ao_syncookie(sk, skb, req, AF_INET); @@ -461,7 +463,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb) flowi4_init_output(&fl4, ireq->ir_iif, ireq->ir_mark, ip_sock_rt_tos(sk), ip_sock_rt_scope(sk), IPPROTO_TCP, inet_sk_flowi_flags(sk), - opt->srr ? opt->faddr : ireq->ir_rmt_addr, + (opt && opt->opt.srr) ? opt->opt.faddr : ireq->ir_rmt_addr, ireq->ir_loc_addr, th->source, th->dest, sk_uid(sk)); security_req_classify_flow(req, flowi4_to_flowi_common(&fl4)); @@ -470,6 +472,12 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb) SKB_DR_SET(reason, IP_OUTNOROUTES); goto out_free; } + /* Same check as in inet_csk_route_req(). */ + if (opt && opt->opt.is_strictroute && rt->rt_uses_gateway) { + ip_rt_put(rt); + SKB_DR_SET(reason, IP_OUTNOROUTES); + goto out_free; + } /* Try to redo what tcp_v4_send_synack did. */ req->rsk_window_clamp = READ_ONCE(tp->window_clamp) ? : -- 2.53.0