css遮罩层上面跟底层会一起移动，大佬们怎么解决的?[问题已解决]

css代码:

<style type="text/css">
body
{
 width:100%;
height: 100%;
 margin: 0px;
   padding:0px;
   background-image: url('【背景】'); 
   background-position: center; 
   background-repeat: no-repeat; 
   background-attachment: fixed; 
   background-size:100% 100%;
   overflow:auto;
}
.zhezhao
{
position: fixed;
left: 0px;
top: 0px;
     right: 0px;
     bottom: 0px;
background: #ffffff;
  position:absolute;
z-index:1001;
width: 100%;
height: 100%;
text-align: center;
}
.tankuang
{
 left: 0px;
top: 0px;
     right: 0px;
     bottom: 0px;
position: relative;
  overflow:auto;
background:#ffffff;
background-image: url('【背景】');
 background-position: center;
 background-repeat: no-repeat; 
 background-attachment: fixed; 
 background-size:100% 100%;
position:absolute;
z-index:1002;
width: 100%;
 height:100%;
border-radius: 5px;
margin: 0 auto;
paddimg:5px;
text-align: center;
}
#header-right
{
position:absolute;
  z-index:1003;
border-radius: 90px;
background:#c0c0c0;
color:#000000;
right: 2px;
top: 0px;
letter-spacing:1px;
  font-size:40px;
  border-style:dotted;
  border-width:2px;
  border-color:#ffffff;
text-align: center;
padding-left:18px;
padding-right:18px;
opacity:0.8;
}
</style>


怎么解决遮罩层跟底层一起移动问题?底层滚动上面一层也跟着动，遮罩层怎么才能全屏?移动端的，有没有解决办法，大家😂百度了好久找不到办法