2007-11-07 21:49:18

by Anthony Liguori

[permalink] [raw]
Subject: [PATCH] Fix used_idx wrap-around in virtio

The more_used() function compares the vq->vring.used->idx with last_used_idx.
Since vq->vring.used->idx is a 16-bit integer, and last_used_idx is an
unsigned int, this results in unpredictable behavior when vq->vring.used->idx
wraps around.

This patch corrects this by changing last_used_idx to the correct type.

Signed-off-by: Anthony Liguori <[email protected]>

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 0e4baca..0e1bf05 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -53,7 +53,7 @@ struct vring_virtqueue
unsigned int num_added;

/* Last used index we've seen. */
- unsigned int last_used_idx;
+ u16 last_used_idx;

/* How to notify other side. FIXME: commonalize hcalls! */
void (*notify)(struct virtqueue *vq);