From a1ca7a12ff70e85a1749c179d38c10ec3cb52b4f Mon Sep 17 00:00:00 2001
From: Dariusz Stojaczyk <dariuszx.stojaczyk@intel.com>
Date: Fri, 22 Dec 2017 11:15:53 +0100
Subject: [PATCH] virtio: fix enqueuing zero-length descriptor chains

Previous descriptor chain was being corrupted
by setting invalid vq->req_end (virtio.c:538).

Change-Id: I4b27db02dc990e6af011a1b614e30e3050379e9f
Signed-off-by: Dariusz Stojaczyk <dariuszx.stojaczyk@intel.com>
Reviewed-on: https://review.gerrithub.io/392774
Reviewed-by: Daniel Verkamp <daniel.verkamp@intel.com>
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
---
 lib/virtio/virtio.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/virtio/virtio.c b/lib/virtio/virtio.c
index 15a954f99..6906e40c7 100644
--- a/lib/virtio/virtio.c
+++ b/lib/virtio/virtio.c
@@ -511,7 +511,8 @@ virtqueue_req_add_iovs(struct virtqueue *vq, struct iovec *iovs, uint16_t iovcnt
 	 * or the caller specifies SPDK_VIRTIO_DESC_F_INDIRECT
 	 */
 
-	prev_head = new_head = vq->vq_desc_head_idx;
+	prev_head = vq->req_end;
+	new_head = vq->vq_desc_head_idx;
 	for (i = 0; i < iovcnt; ++i) {
 		desc = &vq->vq_ring.desc[new_head];