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Tsirkin" To: Jason Wang Cc: virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, xieyongji@bytedance.com, stefanha@redhat.com, file@sect.tu-berlin.de, ashish.kalra@amd.com, konrad.wilk@oracle.com, kvm@vger.kernel.org, hch@infradead.org, ak@linux.intel.com, luto@kernel.org Subject: Re: [PATCH 0/7] Do not read from descriptor ring Message-ID: <20210711120824-mutt-send-email-mst@kernel.org> References: <20210604055350.58753-1-jasowang@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210604055350.58753-1-jasowang@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 04, 2021 at 01:53:43PM +0800, 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]. > > To protect from a malicous device, this series store and use the > descriptor metadata in an auxiliay structure which can not be accessed > via swiotlb/device instead of the ones in the descriptor table. This > means the descriptor table is write-only from the view of the driver. > > Actually, we've almost achieved that through packed virtqueue and we > just need to fix a corner case of handling mapping errors. For split > virtqueue we just follow what's done in the packed. > > Note that we don't duplicate descriptor medata for indirect > descriptors since it uses stream mapping which is read only so it's > safe if the metadata of non-indirect descriptors are correct. > > For split virtqueue, the change increase the footprint due the the > auxiliary metadata but it's almost neglectlable in simple test like > pktgen and netperf TCP stream (slightly noticed in a 40GBE environment > with more CPU usage). > > Slightly tested with packed on/off, iommu on/of, swiotlb force/off in > the guest. > > Note that this series tries to fix the attack via descriptor > ring. The other cases (used ring and config space) will be fixed by > other series or patches. > > Please review. This needs a rebase - can you do it pls? > Changes from RFC V2: > - no code change > - twaeak the commit log a little bit > > Changes from RFC V1: > - Always use auxiliary metadata for split virtqueue > - Don't read from descripto when detaching indirect descriptor > > Jason Wang (7): > virtio-ring: maintain next in extra state for packed virtqueue > virtio_ring: rename vring_desc_extra_packed > virtio-ring: factor out desc_extra allocation > virtio_ring: secure handling of mapping errors > virtio_ring: introduce virtqueue_desc_add_split() > virtio: use err label in __vring_new_virtqueue() > virtio-ring: store DMA metadata in desc_extra for split virtqueue > > drivers/virtio/virtio_ring.c | 201 +++++++++++++++++++++++++---------- > 1 file changed, 144 insertions(+), 57 deletions(-) > > -- > 2.25.1