[PATCH 5/6] virtio: fail adding buffer on broken queues.

[Rusty Russell <rusty@rustcorp.com.au>]

Heinz points out that adding buffers to a broken virtqueue (which
should "never happen") still works.  Failing allows drivers to detect
and complain about broken devices.

Now drivers are robust, we can add this extra check.

Reported-by: Heinz Graalfs <graalfs@linux.vnet.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 drivers/virtio/virtio_ring.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 28b5338fff71..b74033dca384 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -203,6 +203,11 @@ static inline int virtqueue_add(struct virtqueue *_vq,
 
 	BUG_ON(data == NULL);
 
+	if (unlikely(vq->broken)) {
+		END_USE(vq);
+		return -EIO;
+	}
+
 #ifdef DEBUG
 	{
 		ktime_t now = ktime_get();
@@ -309,7 +314,7 @@ add_head:
  * Caller must ensure we don't call this with other virtqueue operations
  * at the same time (except where noted).
  *
- * Returns zero or a negative error (ie. ENOSPC, ENOMEM).
+ * Returns zero or a negative error (ie. ENOSPC, ENOMEM, EIO).
  */
 int virtqueue_add_sgs(struct virtqueue *_vq,
 		      struct scatterlist *sgs[],
@@ -347,7 +352,7 @@ EXPORT_SYMBOL_GPL(virtqueue_add_sgs);
  * Caller must ensure we don't call this with other virtqueue operations
  * at the same time (except where noted).
  *
- * Returns zero or a negative error (ie. ENOSPC, ENOMEM).
+ * Returns zero or a negative error (ie. ENOSPC, ENOMEM, EIO).
  */
 int virtqueue_add_outbuf(struct virtqueue *vq,
 			 struct scatterlist sg[], unsigned int num,
@@ -369,7 +374,7 @@ EXPORT_SYMBOL_GPL(virtqueue_add_outbuf);
  * Caller must ensure we don't call this with other virtqueue operations
  * at the same time (except where noted).
  *
- * Returns zero or a negative error (ie. ENOSPC, ENOMEM).
+ * Returns zero or a negative error (ie. ENOSPC, ENOMEM, EIO).
  */
 int virtqueue_add_inbuf(struct virtqueue *vq,
 			struct scatterlist sg[], unsigned int num,
-- 
1.8.3.2