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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 A44F5C433B4 for ; Fri, 16 Apr 2021 02:58:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 844F961152 for ; Fri, 16 Apr 2021 02:58:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236771AbhDPC7F (ORCPT ); Thu, 15 Apr 2021 22:59:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60486 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234764AbhDPC7E (ORCPT ); Thu, 15 Apr 2021 22:59:04 -0400 Received: from mail-ej1-x633.google.com (mail-ej1-x633.google.com [IPv6:2a00:1450:4864:20::633]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EFF43C061574 for ; Thu, 15 Apr 2021 19:58:38 -0700 (PDT) Received: by mail-ej1-x633.google.com with SMTP id r9so39927114ejj.3 for ; Thu, 15 Apr 2021 19:58:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=h0yx5dLbv8rJZ5DCE5zdmaVWrPKFcLlOvqXcXEtQJwE=; b=tbJgN+AdMgDnjaLBifhtEFNZxnL7ynwTAMqglnR2mQ2OZupVsnB1ZWli4n80gNSFal CtVnloJrfet3S+QHctq8IXgCgyLFZsSWMxbxkNdBalgXIodKaEQlL6tnTxzUfPs4FE+d uY955LpqXDlJZqT7otwymIeBsRD1PuaxbkyOsurMW1BGnEMCrqemYTyHtor/TnJEuDLm wDQpDhY/3sQQ3sWKPupnEIZV4SYN3ErVLbFSMXKqoA+SSAV9TxY6CMkpIT9suwdsgGAI HOUdKobAWx1RU9WsBTKT6m8sdJH9C3U3qRAKTyBUYvpPQeRseZ+VJLqJbGuAnmDo+9Si DbaA== 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=h0yx5dLbv8rJZ5DCE5zdmaVWrPKFcLlOvqXcXEtQJwE=; b=UQz0CyNGwv3cqxBX2XZu4krFIKhtO7tPFVbLJQee+SujR6EwwHluTpQrsmgivUpxGo CHOZrU5uQHSqNedk+yTnxYf1XpGZ6EDwJ2568C8BOqUZLM85R8YKDSBdaGiF4jhCFCfT fKBozPnOAmut1jRUrgLmonidcKU3QG6y0YjKBtpOQWFbU39L1urM4xajs2ATHhU5tR5+ vx1mvmkM0NONLvTlDUS2f/0zyBvkM1j3fYIfzjZA3I32Z0FhVyYDEhC8bc4Yg/XIa4td QhFR9wkGJufHlwvfHXcrGkfhxwKa4bfPzQCksEVdmHswUX2Wqma16J9nyFK02AZvSn+T BXaA== X-Gm-Message-State: AOAM530UYdo0s38QWc6Eu1LBG9X6Ms61SKR6CsFwPNn2uZ5N2AmrFLDE FsWsoSgAlPlbE5tFQL/ufUI6bNBD7TI9vFcUnjHp X-Google-Smtp-Source: ABdhPJz7eIBRH8VgX2Zmf/UNErq4oU3Co9Ax6yOSZDoZbVBaR5IrNHQzKXw8PfZCO8wGmn+eYyHmnqnwdcPMdQf5ERg= X-Received: by 2002:a17:906:1a0d:: with SMTP id i13mr6143661ejf.197.1618541917734; Thu, 15 Apr 2021 19:58:37 -0700 (PDT) MIME-Version: 1.0 References: <20210331080519.172-1-xieyongji@bytedance.com> <20210331080519.172-11-xieyongji@bytedance.com> <80b31814-9e41-3153-7efb-c0c2fab44feb@redhat.com> <02c19c22-13ea-ea97-d99b-71edfee0b703@redhat.com> <5beabeaf-52a6-7ee5-b666-f3616ea82811@redhat.com> In-Reply-To: <5beabeaf-52a6-7ee5-b666-f3616ea82811@redhat.com> From: Yongji Xie Date: Fri, 16 Apr 2021 10:58:26 +0800 Message-ID: Subject: Re: Re: [PATCH v6 10/10] Documentation: Add documentation for VDUSE To: Jason Wang Cc: Stefan Hajnoczi , "Michael S. Tsirkin" , Stefano Garzarella , Parav Pandit , Christoph Hellwig , Christian Brauner , Randy Dunlap , Matthew Wilcox , viro@zeniv.linux.org.uk, Jens Axboe , bcrl@kvack.org, Jonathan Corbet , =?UTF-8?Q?Mika_Penttil=C3=A4?= , Dan Carpenter , virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, kvm@vger.kernel.org, linux-fsdevel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Fri, Apr 16, 2021 at 10:20 AM Jason Wang wrote: > > > =E5=9C=A8 2021/4/15 =E4=B8=8B=E5=8D=887:17, Yongji Xie =E5=86=99=E9=81=93= : > > On Thu, Apr 15, 2021 at 5:05 PM Jason Wang wrote: > >> > >> =E5=9C=A8 2021/4/15 =E4=B8=8B=E5=8D=884:36, Jason Wang =E5=86=99=E9=81= =93: > >>>> Please state this explicitly at the start of the document. Existing > >>>> interfaces like FUSE are designed to avoid trusting userspace. > >>> > >>> There're some subtle difference here. VDUSE present a device to kerne= l > >>> which means IOMMU is probably the only thing to prevent a malicous > >>> device. > >>> > >>> > >>>> Therefore > >>>> people might think the same is the case here. It's critical that peo= ple > >>>> are aware of this before deploying VDUSE with virtio-vdpa. > >>>> > >>>> We should probably pause here and think about whether it's possible = to > >>>> avoid trusting userspace. Even if it takes some effort and costs som= e > >>>> performance it would probably be worthwhile. > >>> > >>> Since the bounce buffer is used the only attack surface is the > >>> coherent area, if we want to enforce stronger isolation we need to us= e > >>> shadow virtqueue (which is proposed in earlier version by me) in this > >>> case. But I'm not sure it's worth to do that. > >> > >> > >> So this reminds me the discussion in the end of last year. We need to > >> make sure we don't suffer from the same issues for VDUSE at least > >> > >> https://yhbt.net/lore/all/c3629a27-3590-1d9f-211b-c0b7be152b32@redhat.= com/T/#mc6b6e2343cbeffca68ca7a97e0f473aaa871c95b > >> > >> Or we can solve it at virtio level, e.g remember the dma address inste= ad > >> of depending on the addr in the descriptor ring > >> > > I might miss something. But VDUSE has recorded the dma address during > > dma mapping, so we would not do bouncing if the addr/length is invalid > > during dma unmapping. Is it enough? > > > E.g malicous device write a buggy dma address in the descriptor ring, so > we had: > > vring_unmap_one_split(desc->addr, desc->len) > dma_unmap_single() > vduse_dev_unmap_page() > vduse_domain_bounce() > > And in vduse_domain_bounce() we had: > > while (size) { > map =3D &domain->bounce_maps[iova >> PAGE_SHIFT]; > offset =3D offset_in_page(iova); > sz =3D min_t(size_t, PAGE_SIZE - offset, size); > > This means we trust the iova which is dangerous and exacly the issue > mentioned in the above link. > > From VDUSE level need to make sure iova is legal. > I think we already do that in vduse_domain_bounce(): while (size) { map =3D &domain->bounce_maps[iova >> PAGE_SHIFT]; if (WARN_ON(!map->bounce_page || map->orig_phys =3D=3D INVALID_PHYS_ADDR)) return; > From virtio level, we should not truse desc->addr. > We would not touch desc->addr after vring_unmap_one_split(). So I'm not sure what we need to do at the virtio level. Thanks, Yongji