How can I block scrolling until the loader displays none?

I was wondering if there's a way to block the scroll bar until a div and its loader gets to the point of display none. I don't know if this can be done just with html or css. Any advice?

 #loader {
    background: #eeeeee;
    bottom: 0;
    height: 100%;
    left: 0;
    right: 0;
    top: 0;
    width: 100%;
    display:block;
    margin: 0 auto;
    position: relative;
    overflow: hidden;
    z-index: 9999;
}
#loaderInner {
    background:#eeeeee url(https://dl.dropboxusercontent.com/s/asdfghfdsas/loader.gif) center center no-repeat;
    background-size: 250px 250px;
    position: absolute;
    height: 250px;
    width: 250px;
    display:block;
    margin: 0 auto;
    top: 50%;
    left: 50%;
    margin: -125px 0px 0px -125px;
}
body#layout #loader {
    display:none;
    overflow: scroll;
}

You can use some simple CSS to prevent scrolling on the page. But you would need to use JS to handle when to apply this class.

CSS

body.loading {
    overflow: hidden;
}