vhost_net: fix wrong iter offset when setting number of buffers

In commit ba7438aed924 ("vhost: don't bother copying iovecs in
handle_rx(), kill memcpy_toiovecend()"), we advance iov iter fixup
sizeof(struct virtio_net_hdr) bytes and fill the number of buffers
after doing the socket recvmsg(). This work well but was broken after
commit 6e03f896b52c ("Merge
git://git.kernel.org/pub/scm/linux/kernel/git/davem/net") which tries
to advance sizeof(struct virtio_net_hdr_mrg_rxbuf). It will fill the
number of buffers at the wrong place. This patch fixes this.

Fixes 6e03f896b52c
("Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net")
Cc: David S. Miller <davem@davemloft.net>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 8dccca9..afa06d2 100644 (file)
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -528,9 +528,9 @@ static void handle_rx(struct vhost_net *net)
                .msg_controllen = 0,
                .msg_flags = MSG_DONTWAIT,
        };
-       struct virtio_net_hdr_mrg_rxbuf hdr = {
-               .hdr.flags = 0,
-               .hdr.gso_type = VIRTIO_NET_HDR_GSO_NONE
+       struct virtio_net_hdr hdr = {
+               .flags = 0,
+               .gso_type = VIRTIO_NET_HDR_GSO_NONE
        };
        size_t total_len = 0;
        int err, mergeable;
@@ -539,6 +539,7 @@ static void handle_rx(struct vhost_net *net)
        size_t vhost_len, sock_len;
        struct socket *sock;
        struct iov_iter fixup;
+       __virtio16 num_buffers;
 
        mutex_lock(&vq->mutex);
        sock = vq->private_data;
@@ -616,9 +617,9 @@ static void handle_rx(struct vhost_net *net)
                }
                /* TODO: Should check and handle checksum. */
 
-               hdr.num_buffers = cpu_to_vhost16(vq, headcount);
+               num_buffers = cpu_to_vhost16(vq, headcount);
                if (likely(mergeable) &&
-                   copy_to_iter(&hdr.num_buffers, 2, &fixup) != 2) {
+                   copy_to_iter(&num_buffers, 2, &fixup) != 2) {
                        vq_err(vq, "Failed num_buffers write");
                        vhost_discard_vq_desc(vq, headcount);
                        break;