On Mon, Jul 13, 2015 at 01:46:51PM +0800, Jason Wang wrote:
> Commit 032a74a1c0fcdd5fd1c69e56126b4c857ee36611
> ("virtio-net: byteswap virtio-net header") breaks any layout by
> requiring out_sg[0].iov_len >= n->guest_hdr_len. Fixing this by
> copying header to temporary buffer and copying it back after byteswap.
>
> Fixes 032a74a1c0fcdd5fd1c69e56126b4c857ee36611
> ("virtio-net: byteswap virtio-net header")
> Cc: qemu-sta...@nongnu.org
> Cc: c...@fr.ibm.com
> Signed-off-by: Jason Wang <jasow...@redhat.com>
> ---
> hw/net/virtio-net.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index e3c2db3..b42af8f 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -1139,10 +1139,11 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q)
> }
>
> while (virtqueue_pop(q->tx_vq, &elem)) {
> - ssize_t ret, len;
> + ssize_t ret, len, s;
> unsigned int out_num = elem.out_num;
> struct iovec *out_sg = &elem.out_sg[0];
> struct iovec sg[VIRTQUEUE_MAX_SIZE];
> + struct virtio_net_hdr hdr;
>
> if (out_num < 1) {
> error_report("virtio-net header not in first element");
> @@ -1150,11 +1151,14 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q)
> }
>
> if (n->has_vnet_hdr) {
> - if (out_sg[0].iov_len < n->guest_hdr_len) {
> + s = iov_to_buf(out_sg, out_num, 0, &hdr, sizeof(hdr));
> + if (s != sizeof(hdr)) {
> error_report("virtio-net header incorrect");
> exit(1);
> }
> - virtio_net_hdr_swap(vdev, (void *) out_sg[0].iov_base);
> + virtio_net_hdr_swap(vdev, (void *) &hdr);
> + s = iov_from_buf(out_sg, out_num, 0, &hdr, sizeof(hdr));
> + assert(s == sizeof(hdr));
> }
>
> /*
Looks like this will write into out_sg - that's violating the virtio spec.
> --
> 2.1.4
