[dpdk-dev] [PATCH] vhost: fix off-by-one error on nr_desc check

[Maxime Coquelin <maxime.coquelin@redhat.com>]

nr_desc is not an index but the number of descriptors,
so can be equal to the virtqueue size.

Fixes: a436f53ebfeb ("vhost: avoid dead loop chain")

Cc: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
Hi Yuanhan,

I faced the bug while testing my indirect descriptor patch, it happens
as soon as the number of chained descritors is above 2.

But the bug may in theory also be faced with normal descriptors, so it might
be good to have it 16.07?

Regards,
Maxime

---
 lib/librte_vhost/vhost_rxtx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c
index bc00518..08a73fd 100644
--- a/lib/librte_vhost/vhost_rxtx.c
+++ b/lib/librte_vhost/vhost_rxtx.c
@@ -748,7 +748,7 @@ copy_desc_to_mbuf(struct virtio_net *dev, struct vhost_virtqueue *vq,
 				break;
 
 			if (unlikely(desc->next >= vq->size ||
-				     ++nr_desc >= vq->size))
+				     ++nr_desc > vq->size))
 				return -1;
 			desc = &vq->desc[desc->next];
 
-- 
2.7.4