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 247D8C433E3 for ; Mon, 20 Jul 2020 15:38:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ED3EA22CB3 for ; Mon, 20 Jul 2020 15:38:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595259501; bh=jdM/Z0ndMFdunOwa0OEBRJHhNEIA6c+prmMqU4DN37w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=ao+WMztthVvI2EJpijgYVxx70EsmFfowVih6weSqz3tAgtuMogOwC6EJ/Nbzoy8IC MtDJCYdGOm8YBBJAEfFhQbjDKWcTZbynopCHmio7NIIxSqYUHGIfN5KJ7ip5b6I4xi suHGO79ynnCGy7iRtUUnH400ELnjwgni/E7tlt8k= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729149AbgGTPiU (ORCPT ); Mon, 20 Jul 2020 11:38:20 -0400 Received: from mail.kernel.org ([198.145.29.99]:56698 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729103AbgGTPiN (ORCPT ); Mon, 20 Jul 2020 11:38:13 -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 B2EDC22CB2; Mon, 20 Jul 2020 15:38:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595259493; bh=jdM/Z0ndMFdunOwa0OEBRJHhNEIA6c+prmMqU4DN37w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gNi0mjlvSgPwTLSaNn6QRGGUijY4GrzvlbYoI5fCLPbvJCWuATgYcfhL7iz+iuZVC AFdob5jp959CzClgFJj4dze+WQrbxG6ai63/R4KSqdW6HeL7+i+e7bs3BCheoQ9B0K MT4qawCn9sZWsz7TcUF/RjtqMJ2KgleQVDYWiT2U= 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 4.4 27/58] tcp: md5: refine tcp_md5_do_add()/tcp_md5_hash_key() barriers Date: Mon, 20 Jul 2020 17:36:43 +0200 Message-Id: <20200720152748.504951306@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200720152747.127988571@linuxfoundation.org> References: <20200720152747.127988571@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 @@ -3088,12 +3088,12 @@ 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); + + /* tcp_md5_do_add() might change key->key under us */ return crypto_hash_update(&hp->md5_desc, &sg, key->keylen); } EXPORT_SYMBOL(tcp_md5_hash_key); --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -931,12 +931,18 @@ 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; } @@ -953,7 +959,7 @@ 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()) {