If "offset" is non-zero then we end up copying from beyond the end of the config because of pointer math. We can fix this by casting the struct to a u8 pointer. Fixes: 2c53d0f64c06 ("vdpasim: vDPA device simulator") Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Link: https://lore.kernel.org/r/20200406144552.GF68494@mwanda Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Acked-by: Jason Wang <jasowang@redhat.com>