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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C668CC433F5 for ; Tue, 12 Oct 2021 05:17:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9350760724 for ; Tue, 12 Oct 2021 05:17:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232387AbhJLFTF (ORCPT ); Tue, 12 Oct 2021 01:19:05 -0400 Received: from szxga01-in.huawei.com ([45.249.212.187]:13722 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231254AbhJLFTF (ORCPT ); Tue, 12 Oct 2021 01:19:05 -0400 Received: from dggemv703-chm.china.huawei.com (unknown [172.30.72.54]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4HT3lK71QFzWdJL; Tue, 12 Oct 2021 13:15:25 +0800 (CST) Received: from dggema772-chm.china.huawei.com (10.1.198.214) by dggemv703-chm.china.huawei.com (10.3.19.46) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2308.8; Tue, 12 Oct 2021 13:17:01 +0800 Received: from huawei.com (10.175.101.6) by dggema772-chm.china.huawei.com (10.1.198.214) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2308.8; Tue, 12 Oct 2021 13:17:00 +0800 From: Liu Jian To: , , , , , , , , , , , , , , , , CC: Subject: [PATHC bpf v2] tcp_bpf: Fix one concurrency problem in the tcp_bpf_send_verdict function Date: Tue, 12 Oct 2021 13:20:19 +0800 Message-ID: <20211012052019.184398-1-liujian56@huawei.com> X-Mailer: git-send-email 2.17.1 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.175.101.6] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggema772-chm.china.huawei.com (10.1.198.214) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org With two Msgs, msgA and msgB and a user doing nonblocking sendmsg calls (or multiple cores) on a single socket 'sk' we could get the following flow. msgA, sk msgB, sk ----------- --------------- tcp_bpf_sendmsg() lock(sk) psock = sk->psock tcp_bpf_sendmsg() lock(sk) ... blocking tcp_bpf_send_verdict if (psock->eval == NONE) psock->eval = sk_psock_msg_verdict .. < handle SK_REDIRECT case > release_sock(sk) < lock dropped so grab here > ret = tcp_bpf_sendmsg_redir psock = sk->psock tcp_bpf_send_verdict lock_sock(sk) ... blocking on B if (psock->eval == NONE) <- boom. psock->eval will have msgA state The problem here is we dropped the lock on msgA and grabbed it with msgB. Now we have old state in psock and importantly psock->eval has not been cleared. So msgB will run whatever action was done on A and the verdict program may never see it. Fixes: 604326b41a6fb ("bpf, sockmap: convert to generic sk_msg interface") Signed-off-by: Liu Jian --- v2: change commit message, and add the fixes tag net/ipv4/tcp_bpf.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c index d3e9386b493e..9d068153c316 100644 --- a/net/ipv4/tcp_bpf.c +++ b/net/ipv4/tcp_bpf.c @@ -232,6 +232,7 @@ static int tcp_bpf_send_verdict(struct sock *sk, struct sk_psock *psock, bool cork = false, enospc = sk_msg_full(msg); struct sock *sk_redir; u32 tosend, delta = 0; + u32 eval = __SK_NONE; int ret; more_data: @@ -275,13 +276,24 @@ static int tcp_bpf_send_verdict(struct sock *sk, struct sk_psock *psock, case __SK_REDIRECT: sk_redir = psock->sk_redir; sk_msg_apply_bytes(psock, tosend); + if (!psock->apply_bytes) { + /* Clean up before releasing the sock lock. */ + eval = psock->eval; + psock->eval = __SK_NONE; + psock->sk_redir = NULL; + } if (psock->cork) { cork = true; psock->cork = NULL; } sk_msg_return(sk, msg, tosend); release_sock(sk); + ret = tcp_bpf_sendmsg_redir(sk_redir, msg, tosend, flags); + + if (eval == __SK_REDIRECT) + sock_put(sk_redir); + lock_sock(sk); if (unlikely(ret < 0)) { int free = sk_msg_free_nocharge(sk, msg); -- 2.17.1