vhost/net: length miscalculation

commit 8b38694a2dc8b18374310df50174f1e4376d6824
    vhost/net: virtio 1.0 byte swap
had this chunk:
-       heads[headcount - 1].len += datalen;
+       heads[headcount - 1].len = cpu_to_vhost32(vq, len - datalen);

This adds datalen with the wrong sign, causing guest panics.

Fixes: 8b38694a2dc8b18374310df50174f1e4376d6824
Reported-by: Alex Williamson <alex.williamson@redhat.com>
Suggested-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 14419a8..d415d69 100644 (file)
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -538,7 +538,7 @@ static int get_rx_bufs(struct vhost_virtqueue *vq,
                ++headcount;
                seg += in;
        }
-       heads[headcount - 1].len = cpu_to_vhost32(vq, len - datalen);
+       heads[headcount - 1].len = cpu_to_vhost32(vq, len + datalen);
        *iovcount = seg;
        if (unlikely(log))
                *log_num = nlogs;