Merge pull request #3472 from qingshi163/fix-slice-overflow

fix #3468 SaturatedSliceIter overflow

vm/src/builtins/slice.rs

@@ -368,13 +368,15 @@ impl SaturatedSliceIter {
 
 impl Iterator for SaturatedSliceIter {
     type Item = usize;
+
     fn next(&mut self) -> Option<Self::Item> {
         if self.len == 0 {
             return None;
         }
         self.len -= 1;
         let ret = self.index as usize;
-        self.index += self.step;
+        // SAFETY: if index is overflowed, len should be zero
+        self.index = self.index.wrapping_add(self.step);
         Some(ret)
     }
 }