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=-14.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,USER_AGENT_SANE_1 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 B34E4C4320A for ; Tue, 17 Aug 2021 04:08:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8BD5660EBD for ; Tue, 17 Aug 2021 04:08:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231192AbhHQEJR (ORCPT ); Tue, 17 Aug 2021 00:09:17 -0400 Received: from out30-133.freemail.mail.aliyun.com ([115.124.30.133]:46632 "EHLO out30-133.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229477AbhHQEJO (ORCPT ); Tue, 17 Aug 2021 00:09:14 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R891e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04394;MF=wenyang@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0UjIiGvt_1629173319; Received: from IT-C02W23QPG8WN.local(mailfrom:wenyang@linux.alibaba.com fp:SMTPD_---0UjIiGvt_1629173319) by smtp.aliyun-inc.com(127.0.0.1); Tue, 17 Aug 2021 12:08:39 +0800 Subject: Re: [PATCH v2 2/2] net: return early for possible invalid uaddr From: Wen Yang To: Eric Dumazet , davem@davemloft.net, David Ahern , Jakub Kicinski , Hideaki YOSHIFUJI Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210811152431.66426-1-wenyang@linux.alibaba.com> <20210811152431.66426-2-wenyang@linux.alibaba.com> <247c8272-0e26-87ab-d492-140047d4abc4@gmail.com> <6c11b9e7-6aac-65c9-4755-99d41fbdcb4e@linux.alibaba.com> Message-ID: Date: Tue, 17 Aug 2021 12:08:39 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <6c11b9e7-6aac-65c9-4755-99d41fbdcb4e@linux.alibaba.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2021/8/13 上午1:35, Wen Yang 写道: > > > 在 2021/8/12 上午12:11, Eric Dumazet 写道: >> >> >> On 8/11/21 5:24 PM, Wen Yang wrote: >>> The inet_dgram_connect() first calls inet_autobind() to select an >>> ephemeral port, then checks uaddr in udp_pre_connect() or >>> __ip4_datagram_connect(), but the port is not released until the socket >>> is closed. This could cause performance issues or even exhaust ephemeral >>> ports if a malicious user makes a large number of UDP connections with >>> invalid uaddr and/or addr_len. >>> >> >> This is a big patch. >> >> Can the malicious user still use a large number of UDP sockets, >> with valid uaddr/add_len and consequently exhaust ephemeral ports ? >> >> If yes, it does not seem your patch is helping. >> > > Thank you for your comments. > However, we could make these optimizations: > > 1, If the user passed in some invalid parameters, we should return as > soon as possible. We shouldn't assume that these parameters are valid > first, then do some real work (such as select an ephemeral port), and > then finally check that they are indeed valid or not. > > 2. Unify the code for checking parameters in udp_pre_connect() and > __ip4_datagram_connect() to make the code clearer. > >> If no, have you tried instead to undo the autobind, if the connect >> fails ? >> > > Thanks. Undo the autobind is useful if the connect fails. > We will add this logic and submit the v3 patch later. > Hello, there is no undo autobind for udp. If this logic is added, the patch will be bigger; maybe we can release this ephemeral port through unhash()? diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c index 8a8dba7..43947d8 100644 --- a/net/ipv4/af_inet.c +++ b/net/ipv4/af_inet.c @@ -563,6 +563,7 @@ int inet_dgram_connect(struct socket *sock, struct sockaddr *uaddr, int addr_len, int flags) { struct sock *sk = sock->sk; + bool autobind; int err; if (addr_len < sizeof(uaddr->sa_family)) @@ -581,9 +582,17 @@ int inet_dgram_connect(struct socket *sock, struct sockaddr *uaddr, return err; } - if (data_race(!inet_sk(sk)->inet_num) && inet_autobind(sk)) + autobind = data_race(!inet_sk(sk)->inet_num); + if (autobind && inet_autobind(sk)) return -EAGAIN; - return sk->sk_prot->connect(sk, uaddr, addr_len); + + err = sk->sk_prot->connect(sk, uaddr, addr_len); + if (err && autobind) { + if (sk->sk_prot->unhash) + sk->sk_prot->unhash(sk); + } + + return err; } EXPORT_SYMBOL(inet_dgram_connect); Could you kindly give some suggestions? In addition, the previous v2 patch detects errors before bind and returns earlier, which should be reasonable. -- Best wishes， Wen