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=-11.6 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL autolearn=no 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 B185EC433E0 for ; Wed, 1 Jul 2020 03:37:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7A73F20748 for ; Wed, 1 Jul 2020 03:37:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="MKVnDFIT" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726765AbgGADhF (ORCPT ); Tue, 30 Jun 2020 23:37:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33950 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725988AbgGADhE (ORCPT ); Tue, 30 Jun 2020 23:37:04 -0400 Received: from mail-yb1-xb41.google.com (mail-yb1-xb41.google.com [IPv6:2607:f8b0:4864:20::b41]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2B98BC03E979 for ; Tue, 30 Jun 2020 20:37:04 -0700 (PDT) Received: by mail-yb1-xb41.google.com with SMTP id o4so11269999ybp.0 for ; Tue, 30 Jun 2020 20:37:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=s3Jq5zLzpbl6Zv3uYHByFe0ZmS4s3FezoDHzT/nIYcQ=; b=MKVnDFITxci7XZwoiI2Qwlr/n6NcWOarH7ex0rhrRXAfYSXZBOstF2ROLvMxeiCDkc UvKCz9Vdfr3s6ws1b6KY39kujwl9Y+TbQTAKz56nj1bk/C9IF2K6EBy38VjZXAulUqWK AXJ4iNasKw/tA0z0uJKYC562PRFKvOkQYrCA1z5o3WqyeBxbM9+1OvbWg8a6pnJX07jK wYkVEeKcmJ5kTb8zi2yOJlT3dY3ns0Df9MbjnkETH48l7DsBe6CveAhPuY/etE2WmxRB CvSJ+ybMGJjV86LvWAFyYC/wRUypUW7ajimzh0ksVFxcPavrKl8HATU2xMMdOdfj2nPA hpEg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=s3Jq5zLzpbl6Zv3uYHByFe0ZmS4s3FezoDHzT/nIYcQ=; b=e5z+PcEJNuT+MU6Ys19SC1oZDImjFk2RNoMH+J++y71yLvBLwxpyDmrpq48ERUY+/N iAxGvD+mrqN/GHdq9hqXR3sTLyzHEIr7Omb/8kGJiY077KNa6enG2ys4atwzxxcER187 bQvJs+LV7ryn2BIqHDS3a3jyS4bCUFIaB/o5zVodUN/dVkVMYGfaOFkTK9zDekH7kz0h jipelo5Xkgud64B5GHGVnX6+x5zMRKNu7MEmm0XueEbl9qpA18z3QNS0JT4ehdxJbM5D UIQxyuPLvAyTytO67JuZ2lHgqNNxSFVUow9GcE20NkdAyeVizdn8tntE/CsLlmCmdKyI /Uhw== X-Gm-Message-State: AOAM5331h2WH85HzmXYasZBmmtiAolxFutbQP3+51iflRUmmwxmKYdeN RIR8eIplVOtRiXBBG+XZ3iaUxVBJ1p1fN6CqIF53Ew== X-Google-Smtp-Source: ABdhPJzptl+ZwuKHWxBxEUKXN0tTbaalbFddIAtD50sheOjj7wa+/JmdyFI74aYBGH2qjkuBhjY6U5OjoVwYPi/KA6U= X-Received: by 2002:a25:b7cc:: with SMTP id u12mr23794552ybj.173.1593574623004; Tue, 30 Jun 2020 20:37:03 -0700 (PDT) MIME-Version: 1.0 References: <20200701020211.GA6875@gondor.apana.org.au> <20200701022241.GA7167@gondor.apana.org.au> <20200701025843.GA7254@gondor.apana.org.au> In-Reply-To: <20200701025843.GA7254@gondor.apana.org.au> From: Eric Dumazet Date: Tue, 30 Jun 2020 20:36:51 -0700 Message-ID: Subject: Re: [regression] TCP_MD5SIG on established sockets To: Herbert Xu Cc: Mathieu Desnoyers , David Miller , Linus Torvalds , LKML , netdev , Yuchung Cheng , Jonathan Rajotte-Julien Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 30, 2020 at 7:59 PM Herbert Xu wrote: > > On Tue, Jun 30, 2020 at 07:30:43PM -0700, Eric Dumazet wrote: > > > > I made this clear in the changelog, do we want comments all over the places ? > > Do not get me wrong, we had this bug for years and suddenly this is a > > big deal... > > I thought you were adding a new pair of smp_rmb/smp_wmb. If they > already exist in the code then I agree it's not a big deal. But > adding a new pair of bogus smp_Xmb's is bad for maintenance. > If I knew so many people were excited about TCP / MD5, I would have posted all my patches on lkml ;) Without the smp_wmb() we would still need something to prevent KMSAN from detecting that we read uninitialized bytes, if key->keylen is increased. (initial content of key->key[] is garbage) Something like this : diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index f111660453241692a17c881dd6dc2910a1236263..c3af8180c7049d5c4987bf5c67e4aff2ed6967c9 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -4033,11 +4033,9 @@ 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); return crypto_ahash_update(hp->md5_req); diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 99916fcc15ca0be12c2c133ff40516f79e6fdf7f..0d08e0134335a21d23702e6a5c24a0f2b3c61c6f 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -1114,9 +1114,13 @@ int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr, /* Pre-existing entry - just update that one. */ 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; } @@ -1132,7 +1136,7 @@ int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr, 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()) {