limiting a child element to parent height, when parent height is not fixed

Question

Is it possible to prevent the overflow of a child in a css grid container set to height: 80% ?

When a css grid row is set to 1fr, it is easily overflown by its children.

My main goal is to limit the height of .bottom & .side,

and have the ul element fill the .side element, while having overflow-y: scroll

.side should always be full height of .bottom.

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body,
html {
  height: 100%;
}

.container {
  height: 80%;
  max-height: 300px;
  width: 500px;
  margin: 0 auto;
  border: 1px solid #000;
  display: grid;
  grid-template-rows: 72px 1fr;
}

.top {
  background-color: cyan;
}

.bottom {
  background-color: #e9eaf4;
  display: grid;
  grid-template-columns: 224px 1fr;
  grid-column-gap: 24px;
}
.bottom .side,
.bottom .main {
  background-color: #fff;
}

ul {
  list-style: none;
  border: 1px dashed red;
}
ul span {
  padding: 10px;
  font-size: 20px;
}

<div class="container">
  <div class="top">top</div>
  <div class="bottom">
    <div class="side">side
    
      <ul>
        <li><span>1</span></li>
        <li><span>2</span></li>
        <li><span>3</span></li>
        <li><span>4</span></li>
        <li><span>5</span></li>
        <li><span>6</span></li>
        <li><span>7</span></li>
        <li><span>8</span></li>
        <li><span>9</span></li>
        <li><span>10</span></li>
      </ul>
    </div>
    <div class="main">main</div>
  </div>
</div>

Answer 1

Adjust the code like below (check the comments). Related question to understand the min-height trick Prevent content from expanding grid items

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body,
html {
  height: 100%;
}

.container {
  height: 80%;
  max-height: 300px;
  width: 500px;
  margin: 0 auto;
  border: 1px solid #000;
  display: grid;
  grid-template-rows: 72px 1fr;
}

.top {
  background-color: cyan;
}

.bottom {
  background-color: #e9eaf4;
  display: grid;
  grid-template-columns: 224px 1fr;
  grid-column-gap: 24px;
  min-height:0; /* added */
}
.bottom .side,
.bottom .main {
  background-color: #fff;
  display:flex; /* added */
  flex-direction:column; /* added */  
  min-height: 0; /* added */
}

ul {
  list-style: none;
  border: 1px dashed red;
  overflow:auto; /* added */
}
ul span {
  padding: 10px;
  font-size: 20px;
}

<div class="container">
  <div class="top">top</div>
  <div class="bottom">
    <div class="side">side
    
      <ul>
        <li><span>1</span></li>
        <li><span>2</span></li>
        <li><span>3</span></li>
        <li><span>4</span></li>
        <li><span>5</span></li>
        <li><span>6</span></li>
        <li><span>7</span></li>
        <li><span>8</span></li>
        <li><span>9</span></li>
        <li><span>10</span></li>
      </ul>
    </div>
    <div class="main">main</div>
  </div>
</div>