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=-8.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,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 9EDF0C2D0DB for ; Thu, 23 Jan 2020 18:06:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7564E21569 for ; Thu, 23 Jan 2020 18:06:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="CLKp+Csb" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729160AbgAWSGp (ORCPT ); Thu, 23 Jan 2020 13:06:45 -0500 Received: from mail-ed1-f67.google.com ([209.85.208.67]:43218 "EHLO mail-ed1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728792AbgAWSGp (ORCPT ); Thu, 23 Jan 2020 13:06:45 -0500 Received: by mail-ed1-f67.google.com with SMTP id dc19so4229216edb.10 for ; Thu, 23 Jan 2020 10:06:44 -0800 (PST) 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:content-transfer-encoding; bh=xq8C26s5Ag4YSRkwj/3ernklbuaULWr84qk69yHOon0=; b=CLKp+Csbefgi5XyeDQuwzjewbW9HMGXtvurOxVeLnW2UoUF08n3BBE2HKGXJ5oMn83 ojk6mw5rwIKdrpaUbsU80JCcyanHGKrkhbK1056J2L04wlvlYVr5c1oHT83Xqnu9tYvY LEwq+GGWlSMZkn0gLmOlRz3EKYXbVhOeIGpMao0fqbZOTMMW/qDn0BprAV7u4qVsPOuI IVlN2iS+vZQdZ+tKb3XCMdh+hjTd0AGr2/tRomOYb4gGw060n3xEkuAodHN5eGbfj1Tf RxdKqQ5fstr0Fh+mDmARYlc74PkAVnXfEuEhyRCQKJdadyLDrRAiptA6KuOTlf2hdBsE LZ/Q== 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:content-transfer-encoding; bh=xq8C26s5Ag4YSRkwj/3ernklbuaULWr84qk69yHOon0=; b=mYr+Rnp+V8/bNY17UwBPthdNqFhHlkgV0nueKjfNo8+JA58Dc+/1t1C33XHDsN/PEQ /NFiXGhhsi+4i7tKH1IQEf60xqN9rLPABqkGgADmXDqJhesQbw5lvD05zqRSZuez2NLh A0706qjyHHcv7qvbWNCXqCQgJJmFtNVkf70aQRnuQs7Xrr0zVElXueMKa9Rl1M1Hs5Q3 0ZvO2WJSI/fTMH7z76Qc9wXnOv08jjts5yBmTUeJaDgDITOU1bOp3A2Ypa+AZZud+gNQ aRnuM+3+G3XCOZU98/hpduGYp8LBfrtPo4z5UDT4qgR7CShyEL2+L46THAkKEyBC90Mj qU1g== X-Gm-Message-State: APjAAAXeaFux89fh5LxjvR3f92WABaYtNyX399BPKE+7RxcSdqCH6Vr8 uMTBBh+0FuoVXdOFcK0OYTDHkq62gcjkHzzlXOyWVw== X-Google-Smtp-Source: APXvYqzjv6a9zpzXpsBg8xzaDyguAXma8w+XOvk37x11FBMKaaEMHF9L6MyHuAJUK4IWOuAUToXe3lbp3DM6Gx+dDKo= X-Received: by 2002:a05:6402:6d2:: with SMTP id n18mr8208132edy.100.1579802803010; Thu, 23 Jan 2020 10:06:43 -0800 (PST) MIME-Version: 1.0 References: <20200122203253.20652-1-lrizzo@google.com> <875zh2bis0.fsf@toke.dk> <953c8fee-91f0-85e7-6c7b-b9a2f8df5aa6@iogearbox.net> <87blqui1zu.fsf@toke.dk> <875zh2hx20.fsf@toke.dk> In-Reply-To: <875zh2hx20.fsf@toke.dk> From: Luigi Rizzo Date: Thu, 23 Jan 2020 10:06:32 -0800 Message-ID: Subject: Re: [PATCH] net-xdp: netdev attribute to control xdpgeneric skb linearization To: =?UTF-8?B?VG9rZSBIw7hpbGFuZC1Kw7hyZ2Vuc2Vu?= Cc: Daniel Borkmann , netdev@vger.kernel.org, Jesper Dangaard Brouer , "David S. Miller" , sameehj@amazon.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, Jan 23, 2020 at 10:01 AM Toke H=C3=B8iland-J=C3=B8rgensen wrote: > > Luigi Rizzo writes: > > > On Thu, Jan 23, 2020 at 8:14 AM Toke H=C3=B8iland-J=C3=B8rgensen wrote: > >> > >> Daniel Borkmann writes: > >> > >> > On 1/23/20 10:53 AM, Toke H=C3=B8iland-J=C3=B8rgensen wrote: > >> >> Luigi Rizzo writes: > >> >> > >> >>> Add a netdevice flag to control skb linearization in generic xdp m= ode. > >> >>> Among the various mechanism to control the flag, the sysfs > >> >>> interface seems sufficiently simple and self-contained. > >> >>> The attribute can be modified through > >> >>> /sys/class/net//xdp_linearize > >> >>> The default is 1 (on) > >> > > >> > Needs documentation in Documentation/ABI/testing/sysfs-class-net. > >> > > >> >> Erm, won't turning off linearization break the XDP program's abilit= y to > >> >> do direct packet access? > >> > > >> > Yes, in the worst case you only have eth header pulled into linear > >> > section. :/ > >> > >> In which case an eBPF program could read/write out of bounds since the > >> verifier only verifies checks against xdp->data_end. Right? > > > > Why out of bounds? Without linearization we construct xdp_buff as follo= ws: > > > > mac_len =3D skb->data - skb_mac_header(skb); > > hlen =3D skb_headlen(skb) + mac_len; > > xdp->data =3D skb->data - mac_len; > > xdp->data_end =3D xdp->data + hlen; > > xdp->data_hard_start =3D skb->data - skb_headroom(skb); > > > > so we shouldn't go out of bounds. > > Hmm, right, as long as it's guaranteed that the bit up to hlen is > already linear; is it? :) honest question: that would be skb->len - skb->data_len, isn't that the linear part by definition ? cheers luigi > > -Toke >