From: Wafer Xie <wa...@jaguarmicro.com>
The virtio-1.2 specification writes:
2.7.6 The Virtqueue Available Ring:
"idx field indicates where the driver would put the next descriptor entry
in the ring (modulo the queue size). This starts at 0, and increases"
The idx will increase from 0 to 0xFFFF and repeat,
So idx may be less than last_avail_idx.
Fixes: 258dc7c96b ("virtio: sanity-check available index")
Signed-off-by: Wafer Xie <wa...@jaguarmicro.com>
--
Changes in v2:
-Modify the commit id of the fix.
---
hw/virtio/virtio.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index a26f18908e..ae7d407113 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -3362,7 +3362,13 @@ virtio_load(VirtIODevice *vdev, QEMUFile *f, int
version_id)
continue;
}
- nheads = vring_avail_idx(&vdev->vq[i]) -
vdev->vq[i].last_avail_idx;
+ if (vring_avail_idx(&vdev->vq[i]) >= vdev->vq[i].last_avail_idx) {
+ nheads = vring_avail_idx(&vdev->vq[i]) -
+ vdev->vq[i].last_avail_idx;
+ } else {
+ nheads = UINT16_MAX - vdev->vq[i].last_avail_idx +
+ vring_avail_idx(&vdev->vq[i]) + 1;
+ }
/* Check it isn't doing strange things with descriptor numbers. */
if (nheads > vdev->vq[i].vring.num) {
virtio_error(vdev, "VQ %d size 0x%x Guest index 0x%x "
--
2.27.0
