Re: [PATCH v3 01/20] virtio: mmio-v1: Validate queue PFN

[Suzuki K Poulose]

Hi Michael,

On 06/29/2018 06:42 PM, Michael S. Tsirkin wrote:
> On Fri, Jun 29, 2018 at 12:15:21PM +0100, Suzuki K Poulose wrote:
> > virtio-mmio with virtio-v1 uses a 32bit PFN for the queue.
> > If the queue pfn is too large to fit in 32bits, which
> > we could hit on arm64 systems with 52bit physical addresses
> > (even with 64K page size), we simply miss out a proper link
> > to the other side of the queue.
> >
> > Add a check to validate the PFN, rather than silently breaking
> > the devices.
> >
> > Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
> > Cc: Jason Wang <jasowang@xxxxxxxxxx>
> > Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
> > Cc: Christoffer Dall <cdall@xxxxxxxxxx>
> > Cc: Peter Maydel <peter.maydell@xxxxxxxxxx>
> > Cc: Jean-Philippe Brucker <jean-philippe.brucker@xxxxxxx>
> > Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> > ---
> > Changes since v2:
> >   - Change errno to -E2BIG
> > ---
> >   drivers/virtio/virtio_mmio.c | 18 ++++++++++++++++--
> >   1 file changed, 16 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
> > index 67763d3..82cedc8 100644
> > --- a/drivers/virtio/virtio_mmio.c
> > +++ b/drivers/virtio/virtio_mmio.c
> > @@ -397,9 +397,21 @@ static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned index,
> >   	/* Activate the queue */
> >   	writel(virtqueue_get_vring_size(vq), vm_dev->base + VIRTIO_MMIO_QUEUE_NUM);
> >   	if (vm_dev->version == 1) {
> > +		u64 q_pfn = virtqueue_get_desc_addr(vq) >> PAGE_SHIFT;
> > +
> > +		/*
> > +		 * virtio-mmio v1 uses a 32bit QUEUE PFN. If we have something
> > +		 * that doesn't fit in 32bit, fail the setup rather than
> > +		 * pretending to be successful.
> > +		 */
> > +		if (q_pfn >> 32) {
> > +			dev_err(&vdev->dev, "virtio-mmio: queue address too large\n");
>
> How about:
> 	"hypervisor bug: legacy virtio-mmio must not be used with more than 0x%llx Gigabytes of memory",
> 	0x1ULL << (32 - 30) << PAGE_SHIFT

nit : Do we need change "hypervisor" => "platform" ? Virtio is used by 
other tools (e.g, emulators) and not just virtual machines.

Suzuki