Virtualization - Aug 2022 - [PATCH] virtio/virtio_pci_legacy: debug checking for queue size

Legacy virtio pci has no way to communicate a change in vq size to
the hypervisor. If ring sizes don't match hypervisor will happily
corrupt memory.

We add a check to vring size before calling
vp_legacy_set_queue_address(). Checking the memory range directly is a
bit cumbersome.

Signed-off-by: Xuan Zhuo <xuanzhuo at linux.alibaba.com>
---
 drivers/virtio/virtio_pci_legacy.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/virtio/virtio_pci_legacy.c
b/drivers/virtio/virtio_pci_legacy.c
index 2257f1b3d8ae..a1553abc45f9 100644
--- a/drivers/virtio/virtio_pci_legacy.c
+++ b/drivers/virtio/virtio_pci_legacy.c
@@ -146,6 +146,12 @@ static struct virtqueue *setup_vq(struct virtio_pci_device
*vp_dev,
 		goto out_del_vq;
 	}
 
+	/* Legacy virtio pci has no way to communicate a change in vq size to
+	 * the hypervisor. If ring sizes don't match hypervisor will happily
+	 * corrupt memory.
+	 */
+	BUG_ON(num != virtqueue_get_vring_size(vq));
+
 	/* activate the queue */
 	vp_legacy_set_queue_address(&vp_dev->ldev, index, q_pfn);
 
-- 
2.31.0