vhost: Fix vhost_copy_to_user()

vhost_copy_to_user is used to copy vring used elements to userspace.
We should use VHOST_ADDR_USED instead of VHOST_ADDR_DESC.

Fixes: f889491 ("vhost: introduce O(1) vq metadata cache")
Signed-off-by: Eric Auger <[email protected]>
Acked-by: Jason Wang <[email protected]>
Acked-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

Author: eauger

drivers/vhost/vhost.c

@@ -744,7 +744,7 @@ static int vhost_copy_to_user(struct vhost_virtqueue *vq, void __user *to,
 		struct iov_iter t;
 		void __user *uaddr = vhost_vq_meta_fetch(vq,
 				     (u64)(uintptr_t)to, size,
-				     VHOST_ADDR_DESC);
+				     VHOST_ADDR_USED);
 
 		if (uaddr)
 			return __copy_to_user(uaddr, from, size);