From: Yongji Xie <xieyongji@bytedance.com>
To: Jason Wang <jasowang@redhat.com>
Cc: "Stefan Hajnoczi" <stefanha@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
"Stefano Garzarella" <sgarzare@redhat.com>,
"Parav Pandit" <parav@nvidia.com>,
"Christoph Hellwig" <hch@infradead.org>,
"Christian Brauner" <christian.brauner@canonical.com>,
"Randy Dunlap" <rdunlap@infradead.org>,
"Matthew Wilcox" <willy@infradead.org>,
viro@zeniv.linux.org.uk, "Jens Axboe" <axboe@kernel.dk>,
bcrl@kvack.org, "Jonathan Corbet" <corbet@lwn.net>,
"Mika Penttilä" <mika.penttila@nextfour.com>,
"Dan Carpenter" <dan.carpenter@oracle.com>,
virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org, kvm@vger.kernel.org,
linux-fsdevel@vger.kernel.org
Subject: Re: Re: [PATCH v6 10/10] Documentation: Add documentation for VDUSE
Date: Fri, 16 Apr 2021 11:18:30 +0800 [thread overview]
Message-ID: <CACycT3vuDN0-niZ2yL3JhEW4fYZWEqYKe-tu7rQWpVEOytcDtw@mail.gmail.com> (raw)
In-Reply-To: <17e3312e-686b-c5dd-852d-e9ffb7f4c707@redhat.com>
On Fri, Apr 16, 2021 at 11:03 AM Jason Wang <jasowang@redhat.com> wrote:
>
>
> 在 2021/4/16 上午10:58, Yongji Xie 写道:
> > On Fri, Apr 16, 2021 at 10:20 AM Jason Wang <jasowang@redhat.com> wrote:
> >>
> >> 在 2021/4/15 下午7:17, Yongji Xie 写道:
> >>> On Thu, Apr 15, 2021 at 5:05 PM Jason Wang <jasowang@redhat.com> 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).
>
Oh, yes. Will do it!
>
> >
> >
> >> 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.
>
OK, I see.
Thanks,
Yongji
next prev parent reply other threads:[~2021-04-16 3:18 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-31 8:05 [PATCH v6 00/10] Introduce VDUSE - vDPA Device in Userspace Xie Yongji
2021-03-31 8:05 ` [PATCH v6 01/10] file: Export receive_fd() to modules Xie Yongji
2021-03-31 9:15 ` Christian Brauner
2021-03-31 9:26 ` Dan Carpenter
2021-03-31 9:28 ` Christian Brauner
2021-03-31 11:32 ` Yongji Xie
2021-03-31 12:23 ` Christian Brauner
2021-03-31 13:59 ` Yongji Xie
2021-03-31 14:07 ` Christian Brauner
2021-03-31 14:37 ` Yongji Xie
2021-03-31 8:05 ` [PATCH v6 02/10] eventfd: Increase the recursion depth of eventfd_signal() Xie Yongji
2021-03-31 8:05 ` [PATCH v6 03/10] vhost-vdpa: protect concurrent access to vhost device iotlb Xie Yongji
2021-04-09 16:15 ` Michael S. Tsirkin
2021-04-11 5:36 ` Yongji Xie
2021-04-11 20:48 ` Michael S. Tsirkin
2021-04-12 2:29 ` Yongji Xie
2021-04-12 9:00 ` Michael S. Tsirkin
2021-03-31 8:05 ` [PATCH v6 04/10] vhost-iotlb: Add an opaque pointer for vhost IOTLB Xie Yongji
2021-03-31 8:05 ` [PATCH v6 05/10] vdpa: Add an opaque pointer for vdpa_config_ops.dma_map() Xie Yongji
2021-03-31 8:05 ` [PATCH v6 06/10] vdpa: factor out vhost_vdpa_pa_map() and vhost_vdpa_pa_unmap() Xie Yongji
2021-03-31 8:05 ` [PATCH v6 07/10] vdpa: Support transferring virtual addressing during DMA mapping Xie Yongji
2021-04-08 2:36 ` Jason Wang
2021-03-31 8:05 ` [PATCH v6 08/10] vduse: Implement an MMU-based IOMMU driver Xie Yongji
2021-04-08 3:25 ` Jason Wang
2021-04-08 5:27 ` Yongji Xie
2021-03-31 8:05 ` [PATCH v6 09/10] vduse: Introduce VDUSE - vDPA Device in Userspace Xie Yongji
2021-04-08 6:57 ` Jason Wang
2021-04-08 9:36 ` Yongji Xie
2021-04-09 5:36 ` Jason Wang
2021-04-09 8:02 ` Yongji Xie
2021-04-12 7:16 ` Jason Wang
2021-04-12 8:02 ` Yongji Xie
2021-04-12 9:37 ` Jason Wang
2021-04-12 9:59 ` Yongji Xie
2021-04-13 3:35 ` Jason Wang
2021-04-13 4:28 ` Yongji Xie
2021-04-14 8:18 ` Jason Wang
2021-04-16 3:24 ` Jason Wang
2021-04-16 8:43 ` Yongji Xie
2021-03-31 8:05 ` [PATCH v6 10/10] Documentation: Add documentation for VDUSE Xie Yongji
2021-04-08 7:18 ` Jason Wang
2021-04-08 8:09 ` Yongji Xie
2021-04-14 14:14 ` Stefan Hajnoczi
2021-04-15 5:38 ` Yongji Xie
2021-04-15 7:19 ` Stefan Hajnoczi
2021-04-15 8:33 ` Yongji Xie
2021-04-15 14:17 ` Stefan Hajnoczi
2021-04-15 8:36 ` Jason Wang
2021-04-15 9:04 ` Jason Wang
2021-04-15 11:17 ` Yongji Xie
2021-04-16 2:20 ` Jason Wang
2021-04-16 2:58 ` Yongji Xie
2021-04-16 3:02 ` Jason Wang
2021-04-16 3:18 ` Yongji Xie [this message]
2021-04-15 14:38 ` Stefan Hajnoczi
2021-04-16 2:23 ` Jason Wang
2021-04-16 3:19 ` Yongji Xie
2021-04-16 5:39 ` Jason Wang
2021-04-16 3:13 ` Yongji Xie
2021-04-14 7:34 ` [PATCH v6 00/10] Introduce VDUSE - vDPA Device in Userspace Michael S. Tsirkin
2021-04-14 7:49 ` Jason Wang
2021-04-14 7:54 ` Yongji Xie
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