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 3372CC2D0DB for ; Thu, 23 Jan 2020 17:30:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 06EE421569 for ; Thu, 23 Jan 2020 17:30:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="Ek/tij/M" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729058AbgAWRat (ORCPT ); Thu, 23 Jan 2020 12:30:49 -0500 Received: from mail-ed1-f68.google.com ([209.85.208.68]:42030 "EHLO mail-ed1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728911AbgAWRas (ORCPT ); Thu, 23 Jan 2020 12:30:48 -0500 Received: by mail-ed1-f68.google.com with SMTP id e10so4096815edv.9 for ; Thu, 23 Jan 2020 09:30:47 -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=a4VaNrzbQO1GcIg/YS1YuuopvLPSuKTOR9MEaQWj+og=; b=Ek/tij/MT/WEmu0Vpr7gHtP/F15rfzV+VuE3cSsPdK1xlV8WeH7Eso5wPK7DH25cju JTeIhMLVsg9Ap0ZodKoWqjjNgu0yjUTDZQifmBE06y9+Io6eBhpFp5jxsBS/nc6ht07L 2vTwLrqbkrYpcnqb85pqPvHpGsoccnCaN6OveeNHAM5RzYQ2sKbxMCtaAk2CinIP6eQV rZ5kIIuAxnmzqv1ii7YB8ARAUPNRqigMyJc68CIl3FM2fHOXlIlW4x4LpLtPwB4WC91S MkxOlze5MDoK0N4IPX+Eho5DyaRzjGPo8IgEv6n54eXJWS8bnK2q08T1DxYxpO+4E71R RUdw== 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=a4VaNrzbQO1GcIg/YS1YuuopvLPSuKTOR9MEaQWj+og=; b=TOyJ1Rk7Mynw0zfj4IjEjhQl2ACnlk/6hEXIY1tH/NvtudtrGkpO6Lo40IVyzlnu/T 1I7BAtOC6T2bPX/+5QsD6TyJd7axLlHa/J4D08gBrvGAW3HSYgaVo4OD7rHDw7zNZes5 YcgVGAI1QfUZghtoWy8JXzsS7AKy5/epPTX+VZ63G5/BvkKu25bYoY+3MthjpeJc9E5T YGC9L7UbuLiRSnTP4WMgRzGwaJQOUa6Ll9Ak8/IK7JabXCfXrEkr7rinlYBg/pwIO3CR Q5N5/j9d9JMWW9WNnZKbDZSQpUEAh4Q4NJSAvhmr94PfQ86LudmbNfifoPG4Rbkwqy3A oy5A== X-Gm-Message-State: APjAAAUMLpgdKg7z2CCFbtb0b/KsuKD0VOm5sXc2e4xq45DSQw7mtq+2 CD30loxGbvOzrj6TqJhJuyG2jPZP0JJW4SsaF+L1eg== X-Google-Smtp-Source: APXvYqyt8J67mbrRRHPjFnEk33di/ILv9Vov0CLSM0UC3AbHnxr5gbun7mRalQpffbT8pLbD7t//K2vJlpOoHsSaj9g= X-Received: by 2002:a05:6402:6d2:: with SMTP id n18mr8057043edy.100.1579800646680; Thu, 23 Jan 2020 09:30:46 -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> In-Reply-To: <87blqui1zu.fsf@toke.dk> From: Luigi Rizzo Date: Thu, 23 Jan 2020 09:30:35 -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 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 mode= . > >>> 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 ability t= o > >> 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 follows: 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. cheers luigi