macvtap: advance iov iterator when needed in macvtap_put_user()

When mergeable buffer is used, vnet_hdr_sz is greater than sizeof struct
virtio_net_hdr. So we need advance the iov iterators in this case.

Fixes 6c36d2e26cda1ad3e2c4b90dd843825fc62fe5b4 ("macvtap: Use iovec iterators")
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index cea99d4a8263..42a80d3de839 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -797,6 +797,8 @@ static ssize_t macvtap_put_user(struct macvtap_queue *q,
                 if (copy_to_iter(&vnet_hdr, sizeof(vnet_hdr), iter) !=
                     sizeof(vnet_hdr))
                         return -EFAULT;
+
+                iov_iter_advance(iter, vnet_hdr_len - sizeof(vnet_hdr));
         }
         total = vnet_hdr_len;
         total += skb->len;