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=-6.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=ham 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 24679C4360C for ; Wed, 2 Oct 2019 23:29:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E6A73215EA for ; Wed, 2 Oct 2019 23:29:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="kpc6N+43" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728892AbfJBX3w (ORCPT ); Wed, 2 Oct 2019 19:29:52 -0400 Received: from mail-qk1-f194.google.com ([209.85.222.194]:39474 "EHLO mail-qk1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726798AbfJBX3v (ORCPT ); Wed, 2 Oct 2019 19:29:51 -0400 Received: by mail-qk1-f194.google.com with SMTP id 4so493679qki.6; Wed, 02 Oct 2019 16:29:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=px76N5Ygyt1+IaPaI8lPcGpZkxeisLsbA6YBoyUGZsk=; b=kpc6N+43kHEhQsTbxUhs1VlXqZ/4llzRMyDhVnOUlpAkjcuvRyrD3CjG/lbI3Dktgw O07IgARrj4egPxvsrn6bJTr8MOOXXRvvHr/KgSgTTj7jVJTabWuYFVCGDM4FpcUuItJN JnIh77eBrBBHgmYPtggm9jT6MSii32eedAhVNi/HJSZB+JO8kVEAF71uhfyJwA+X8M5v 6HsZnHnSrMISDX/0znO1VAG3cE0gzxKSvyfQKEPccnHY8Qqny1wV3ZQbRbOAyGpnB7qw eaX5d1OLznV8uLf0exSpqJtE1Yzm0mb36buAWekadlwFTO5aj7YSRoFFJyxW5Ct+mRoI bIBg== 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=px76N5Ygyt1+IaPaI8lPcGpZkxeisLsbA6YBoyUGZsk=; b=a1TfU7kgwOv1pU5hRZIJOSqRDyGmZDxajH7QNPD436Xenl2eRtCssvk0yzspz1rb5U vPizF/zDpsfPDrgYNe5p9PEEIOPZDOe44NtSjlhwrIyd0QK803lGiK+LCY7sbZWyGTDw KRsHPQBPwEQd0PCqIwURD3YARF7MwCPp2RiJb/HAjtOfnp5e6MT5nIz2sHXmPJw82rLn dCI31Lgd1YzBQ7045M3b2IKqjW5TAp/oTkqHm6nrYdJlwzghinJyfM9uikno/LtdOzjB 4+nNRkHMkxp7pcw0V62xLmhsAWZZy6IXNn6LN5YxbrjsFIIoisxIQQqFgsd5JUKrnh71 qhVw== X-Gm-Message-State: APjAAAWGplOT1sZ+QTCa9GPGZWKkG0we5zIezuRAKVSkn38Qt21JyShx Kmh1pemC1jKOsRQDm7ggle7Oh1BbgRDsSFU55XE= X-Google-Smtp-Source: APXvYqyHFJy8nYfCoKUjZpUzSzmYzsMlShEropZlNJ4z2f11vlFDW5/mLSDeK/ebISRMUSZO8n1lT7SO8CF3/OUIM4o= X-Received: by 2002:a37:4e55:: with SMTP id c82mr1479110qkb.437.1570058990712; Wed, 02 Oct 2019 16:29:50 -0700 (PDT) MIME-Version: 1.0 References: <20191002173357.253643-1-sdf@google.com> <20191002173357.253643-2-sdf@google.com> In-Reply-To: <20191002173357.253643-2-sdf@google.com> From: Andrii Nakryiko Date: Wed, 2 Oct 2019 16:29:39 -0700 Message-ID: Subject: Re: [PATCH bpf-next 1/2] bpf/flow_dissector: add mode to enforce global BPF flow dissector To: Stanislav Fomichev Cc: Networking , bpf , "David S. Miller" , Alexei Starovoitov , Daniel Borkmann , Petar Penkov Content-Type: text/plain; charset="UTF-8" Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, Oct 2, 2019 at 10:35 AM Stanislav Fomichev wrote: > > Always use init_net flow dissector BPF program if it's attached and fall > back to the per-net namespace one. Also, deny installing new programs if > there is already one attached to the root namespace. > Users can still detach their BPF programs, but can't attach any > new ones (-EPERM). > > Cc: Petar Penkov > Signed-off-by: Stanislav Fomichev > --- > Documentation/bpf/prog_flow_dissector.rst | 3 +++ > net/core/flow_dissector.c | 11 ++++++++++- > 2 files changed, 13 insertions(+), 1 deletion(-) > > diff --git a/Documentation/bpf/prog_flow_dissector.rst b/Documentation/bpf/prog_flow_dissector.rst > index a78bf036cadd..4d86780ab0f1 100644 > --- a/Documentation/bpf/prog_flow_dissector.rst > +++ b/Documentation/bpf/prog_flow_dissector.rst > @@ -142,3 +142,6 @@ BPF flow dissector doesn't support exporting all the metadata that in-kernel > C-based implementation can export. Notable example is single VLAN (802.1Q) > and double VLAN (802.1AD) tags. Please refer to the ``struct bpf_flow_keys`` > for a set of information that's currently can be exported from the BPF context. > + > +When BPF flow dissector is attached to the root network namespace (machine-wide > +policy), users can't override it in their child network namespaces. > diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c > index 7c09d87d3269..494e2016fe84 100644 > --- a/net/core/flow_dissector.c > +++ b/net/core/flow_dissector.c > @@ -115,6 +115,11 @@ int skb_flow_dissector_bpf_prog_attach(const union bpf_attr *attr, > struct bpf_prog *attached; > struct net *net; > > + if (rcu_access_pointer(init_net.flow_dissector_prog)) { > + /* Can't override root flow dissector program */ > + return -EPERM; > + } This is racy, shouldn't this be checked after grabbing a lock below? > + > net = current->nsproxy->net_ns; > mutex_lock(&flow_dissector_mutex); > attached = rcu_dereference_protected(net->flow_dissector_prog, > @@ -910,7 +915,11 @@ bool __skb_flow_dissect(const struct net *net, > WARN_ON_ONCE(!net); > if (net) { > rcu_read_lock(); > - attached = rcu_dereference(net->flow_dissector_prog); > + attached = > + rcu_dereference(init_net.flow_dissector_prog); > + > + if (!attached) > + attached = rcu_dereference(net->flow_dissector_prog); > > if (attached) { > struct bpf_flow_keys flow_keys; > -- > 2.23.0.444.g18eeb5a265-goog >