From: Jason Wang <jasowang@redhat.com>
Date: Fri, 9 Mar 2018 14:50:33 +0800
Subject: vhost_net: keep private_data and rx_ring synced
Patch-mainline: v4.16-rc7
Git-commit: 303fd71b37fb710b26f5ff5444029d62cfd627bd
References: bsc#1109837

We get pointer ring from the exported sock, this means we should keep
rx_ring and vq->private synced during both vq stop and backend set,
otherwise we may see stale rx_ring.

Fixes: c67df11f6e480 ("vhost_net: try batch dequing from skb array")
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/vhost/net.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -972,6 +972,7 @@ static struct socket *vhost_net_stop_vq(
 	vhost_net_disable_vq(n, vq);
 	vq->private_data = NULL;
 	vhost_net_buf_unproduce(nvq);
+	nvq->rx_ring = NULL;
 	mutex_unlock(&vq->mutex);
 	return sock;
 }
@@ -1161,14 +1162,14 @@ static long vhost_net_set_backend(struct
 		vhost_net_disable_vq(n, vq);
 		vq->private_data = sock;
 		vhost_net_buf_unproduce(nvq);
-		if (index == VHOST_NET_VQ_RX)
-			nvq->rx_ring = get_tap_ptr_ring(fd);
 		r = vhost_vq_init_access(vq);
 		if (r)
 			goto err_used;
 		r = vhost_net_enable_vq(n, vq);
 		if (r)
 			goto err_used;
+		if (index == VHOST_NET_VQ_RX)
+			nvq->rx_ring = get_tap_ptr_ring(fd);
 
 		oldubufs = nvq->ubufs;
 		nvq->ubufs = ubufs;