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=-10.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 AD035C43445 for ; Mon, 20 Jul 2020 16:43:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8E14A2070A for ; Mon, 20 Jul 2020 16:43:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595263398; bh=9YWaCtlFaS/RkIpFOKgFAogxLs9r0cAjS2ySI6Xkhuw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=h5+ceftZmWYObdxonmuuroeLe+zicJ9zEKwHbHAYTh0ju6Lf48em3tsE4QWNobDaw BOf1V+4iYGNnxc7iS9h3nh77c7lqy76PKV5lgZ2i52B0hLuxWBzgkS02kMmvdw3x8V vqECM2pi69EL7dfkSXGstNu/XExrypSeSwF240Ww= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730039AbgGTPmQ (ORCPT ); Mon, 20 Jul 2020 11:42:16 -0400 Received: from mail.kernel.org ([198.145.29.99]:34986 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730029AbgGTPmO (ORCPT ); Mon, 20 Jul 2020 11:42:14 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 678CA20773; Mon, 20 Jul 2020 15:42:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595259734; bh=9YWaCtlFaS/RkIpFOKgFAogxLs9r0cAjS2ySI6Xkhuw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BgG5Gi4a1/oholFu9zn0REtV0Ua/t7zuXzL/M47tmfrTas0BYifMXXaURVQ/NvD9N afF49LpfDvERnAwBE0124GFGmKcSFQPmObpNhsH189fwi6LGt7Avbc/+dNQMdahfiA +mbyg0/mSHc8gERFQOlSxutLu5F0x87rRpbgoeRg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Mathieu Desnoyers , Herbert Xu , Marco Elver , "David S. Miller" Subject: [PATCH 4.9 33/86] tcp: md5: refine tcp_md5_do_add()/tcp_md5_hash_key() barriers Date: Mon, 20 Jul 2020 17:36:29 +0200 Message-Id: <20200720152754.820313288@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200720152753.138974850@linuxfoundation.org> References: <20200720152753.138974850@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Eric Dumazet [ Upstream commit e6ced831ef11a2a06e8d00aad9d4fc05b610bf38 ] My prior fix went a bit too far, according to Herbert and Mathieu. Since we accept that concurrent TCP MD5 lookups might see inconsistent keys, we can use READ_ONCE()/WRITE_ONCE() instead of smp_rmb()/smp_wmb() Clearing all key->key[] is needed to avoid possible KMSAN reports, if key->keylen is increased. Since tcp_md5_do_add() is not fast path, using __GFP_ZERO to clear all struct tcp_md5sig_key is simpler. data_race() was added in linux-5.8 and will prevent KCSAN reports, this can safely be removed in stable backports, if data_race() is not yet backported. v2: use data_race() both in tcp_md5_hash_key() and tcp_md5_do_add() Fixes: 6a2febec338d ("tcp: md5: add missing memory barriers in tcp_md5_do_add()/tcp_md5_hash_key()") Signed-off-by: Eric Dumazet Cc: Mathieu Desnoyers Cc: Herbert Xu Cc: Marco Elver Reviewed-by: Mathieu Desnoyers Acked-by: Herbert Xu Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv4/tcp.c | 6 +++--- net/ipv4/tcp_ipv4.c | 14 ++++++++++---- 2 files changed, 13 insertions(+), 7 deletions(-) --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -3207,13 +3207,13 @@ EXPORT_SYMBOL(tcp_md5_hash_skb_data); int tcp_md5_hash_key(struct tcp_md5sig_pool *hp, const struct tcp_md5sig_key *key) { - u8 keylen = key->keylen; + u8 keylen = READ_ONCE(key->keylen); /* paired with WRITE_ONCE() in tcp_md5_do_add */ struct scatterlist sg; - smp_rmb(); /* paired with smp_wmb() in tcp_md5_do_add() */ - sg_init_one(&sg, key->key, keylen); ahash_request_set_crypt(hp->md5_req, &sg, NULL, keylen); + + /* tcp_md5_do_add() might change key->key under us */ return crypto_ahash_update(hp->md5_req); } EXPORT_SYMBOL(tcp_md5_hash_key); --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -936,12 +936,18 @@ int tcp_md5_do_add(struct sock *sk, cons key = tcp_md5_do_lookup(sk, addr, family); if (key) { - /* Pre-existing entry - just update that one. */ + /* Pre-existing entry - just update that one. + * Note that the key might be used concurrently. + */ memcpy(key->key, newkey, newkeylen); - smp_wmb(); /* pairs with smp_rmb() in tcp_md5_hash_key() */ + /* Pairs with READ_ONCE() in tcp_md5_hash_key(). + * Also note that a reader could catch new key->keylen value + * but old key->key[], this is the reason we use __GFP_ZERO + * at sock_kmalloc() time below these lines. + */ + WRITE_ONCE(key->keylen, newkeylen); - key->keylen = newkeylen; return 0; } @@ -957,7 +963,7 @@ int tcp_md5_do_add(struct sock *sk, cons rcu_assign_pointer(tp->md5sig_info, md5sig); } - key = sock_kmalloc(sk, sizeof(*key), gfp); + key = sock_kmalloc(sk, sizeof(*key), gfp | __GFP_ZERO); if (!key) return -ENOMEM; if (!tcp_alloc_md5sig_pool()) {