[PATCH trivial] vu_common: Detach element from virtqueue on invalid TX buffer

[Laurent Vivier <lvivier@redhat.com>]

When vu_queue_pop() succeeds but the element contains no out buffers,
we warn and break out of the TX loop.  However, vu_queue_pop() already
incremented vq->inuse for this element.  Since we don't add it to the
count of elements to be filled and flushed back to the guest, the
inuse counter is left inconsistent.

Call vu_queue_detach_element() before breaking to decrement vq->inuse
and properly release the element.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
---
 vu_common.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/vu_common.c b/vu_common.c
index 5f2ce18e5b71..ff8f1c046026 100644
--- a/vu_common.c
+++ b/vu_common.c
@@ -190,6 +190,7 @@ static void vu_handle_tx(struct vu_dev *vdev, int index,
 
 		if (elem[count].out_num < 1) {
 			warn("virtio-net transmit queue contains no out buffers");
+			vu_queue_detach_element(vq);
 			break;
 		}
 
-- 
2.53.0