How to make bootstrap column height to 100% row height?

I haven't found a suitable solution to this and it seems so trivial.

I have two columns inside a row:

<div class="row">
  <div class="col-xs-9">
    <div class="left-side">
      <p>sdfsdf</p>
      <p>sdfsdf</p>
      <p>sdfsdf</p>
    </div>
  </div>
  <div class="col-xs-3">
    <div class="something">asdfdf</div>
  </div>
</div>

The row height is set by the larger row, left-side. However, I want the right side's height to be the same.

This seems intuitive, but it doesn't work

.left-side {
    background-color: blue;
}
.something {
    height: 100%;
    background-color: red;
}
.row {
    background-color: green;
}

http://jsfiddle.net/ccorcos/jz8j247x/

You can solve that using display table.

Here is the updated JSFiddle that solves your problem.

CSS

.body {
    display: table;
    background-color: green;
}

.left-side {
    background-color: blue;
    float: none;
    display: table-cell;
    border: 1px solid;
}

.right-side {
    background-color: red;
    float: none;
    display: table-cell;
    border: 1px solid;
}

HTML

<div class="row body">
        <div class="col-xs-9 left-side">
            <p>sdfsdf</p>
            <p>sdfsdf</p>
            <p>sdfsdf</p>
            <p>sdfsdf</p>
            <p>sdfsdf</p>
            <p>sdfsdf</p>
        </div>
        <div class="col-xs-3 right-side">
            asdfdf
        </div>
    </div>

@Alan's answer will do what you're looking for, but this solution fails when you use the responsive capabilities of Bootstrap. In your case, you're using the xs sizes so you won't notice, but if you used anything else (e.g. col-sm, col-md, etc), you'd understand.

Another approach is to play with margins and padding. See the updated fiddle: http://jsfiddle.net/jz8j247x/1/

.left-side {
  background-color: blue;
  padding-bottom: 1000px;
  margin-bottom: -1000px;
  height: 100%;
}
.something {
  height: 100%;
  background-color: red;
  padding-bottom: 1000px;
  margin-bottom: -1000px;
  height: 100%;
}
.row {
  background-color: green;
  overflow: hidden;
}