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

From: Suzuki K Poulose
Date: Tue Jul 03 2018 - 04:03:51 EST

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.