virtio: ignore corrupted virtqueues rather than spinning.

A corrupt virtqueue (caused by the other end screwing up) can have
strange results such as a driver spinning: just bail when we try to
get a buffer from a known-broken queue.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index c2fa5c6..937a49d 100644 (file)
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -184,6 +184,11 @@ static void *vring_get_buf(struct virtqueue *_vq, unsigned int *len)
 
        START_USE(vq);
 
+       if (unlikely(vq->broken)) {
+               END_USE(vq);
+               return NULL;
+       }
+
        if (!more_used(vq)) {
                pr_debug("No more buffers in queue\n");
                END_USE(vq);