linux-kernel - Re: [PATCH 0/7] Do not read from descriptor ring

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Message-ID: <1c079daa-f73d-cb1a-15ef-d8f57f9813b8@kernel.org>
Date:   Tue, 8 Jun 2021 09:24:04 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Jason Wang <jasowang@...hat.com>, mst@...hat.com
Cc:     virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, xieyongji@...edance.com,
        stefanha@...hat.com, file@...t.tu-berlin.de, ashish.kalra@....com,
        konrad.wilk@...cle.com, kvm@...r.kernel.org, hch@...radead.org,
        ak@...ux.intel.com
Subject: Re: [PATCH 0/7] Do not read from descriptor ring

On 6/3/21 10:53 PM, Jason Wang wrote:
> Hi:
> 
> The virtio driver should not trust the device. This beame more urgent
> for the case of encrtpyed VM or VDUSE[1]. In both cases, technology
> like swiotlb/IOMMU is used to prevent the poking/mangling of memory
> from the device. But this is not sufficient since current virtio
> driver may trust what is stored in the descriptor table (coherent
> mapping) for performing the DMA operations like unmap and bounce so
> the device may choose to utilize the behaviour of swiotlb to perform
> attacks[2].

Based on a quick skim, this looks entirely reasonable to me.

(I'm not a virtio maintainer or expert.  I got my hands very dirty with
virtio once dealing with the DMA mess, but that's about it.)

--Andy