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=-7.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 54379C433ED for ; Fri, 16 Apr 2021 03:03:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2B47261152 for ; Fri, 16 Apr 2021 03:03:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235937AbhDPDDq (ORCPT ); Thu, 15 Apr 2021 23:03:46 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:43948 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234764AbhDPDDo (ORCPT ); Thu, 15 Apr 2021 23:03:44 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618542200; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ikyH2z8Vt7uMI/VG6XB6eSk4QGEm2QFd/gz535ClrYI=; b=LME/u4BdDS2d6uVI+gvTjLYA0fTc9mkKVcHkc0XLoeFyEUA8Y01lWUtAysPZiocbi0hbyE v373lnXB3REEuJ8KTgnJw5Dan0TwraVoBqNzQ5UJjMQ5eh9C34DDKtjSTLss8k0hlseQoj Txd/sSk5h9svb/OdjYxjKabJmAEYlIg= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-68-ByMz4XzrPpGli7s2BmtqTA-1; Thu, 15 Apr 2021 23:03:16 -0400 X-MC-Unique: ByMz4XzrPpGli7s2BmtqTA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8D9EB81744F; Fri, 16 Apr 2021 03:03:14 +0000 (UTC) Received: from wangxiaodeMacBook-Air.local (ovpn-13-140.pek2.redhat.com [10.72.13.140]) by smtp.corp.redhat.com (Postfix) with ESMTP id F395B60BE5; Fri, 16 Apr 2021 03:02:58 +0000 (UTC) Subject: Re: [PATCH v6 10/10] Documentation: Add documentation for VDUSE To: Yongji Xie 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 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> From: Jason Wang Message-ID: <17e3312e-686b-c5dd-852d-e9ffb7f4c707@redhat.com> Date: Fri, 16 Apr 2021 11:02:57 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org 在 2021/4/16 上午10:58, Yongji Xie 写道: > On Fri, Apr 16, 2021 at 10:20 AM Jason Wang wrote: >> >> 在 2021/4/15 下午7:17, Yongji Xie 写道: >>> On Thu, Apr 15, 2021 at 5:05 PM Jason Wang wrote: >>>> 在 2021/4/15 下午4:36, Jason Wang 写道: >>>>>> 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 kernel >>>>> 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 people >>>>>> 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 some >>>>>> 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 use >>>>> 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 instead >>>> 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 = &domain->bounce_maps[iova >> PAGE_SHIFT]; >> offset = offset_in_page(iova); >> sz = 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 = &domain->bounce_maps[iova >> PAGE_SHIFT]; > > if (WARN_ON(!map->bounce_page || > map->orig_phys == INVALID_PHYS_ADDR)) > return; So you don't check whether iova is legal before using it, so it's at least a possible out of bound access of the bounce_maps[] isn't it? (e.g what happens if iova is ULLONG_MAX). > > >> 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. I think the point is to record the dma addres/len somewhere instead of reading them from descriptor ring. Thanks > > Thanks, > Yongji >