Add checked arithmetic to prevent integer overflow in dense trie lookups #7442
Description
Description
The ZeroAsciiDenseSparse2dTrieBorrowed::get() method currently uses unchecked arithmetic for matrix index calculations and value additions. This could potentially cause integer overflow on edge cases or with malformed data.
Current Code
File: utils/zerotrie/src/dense.rs
let suffix_count = usize::from(self.suffix_count);
let Some(offset) = self.dense.get(suffix_count * row_index + column_index) else {
// The row and column indexes should be in-range
debug_assert!(false);
return None;
};
// ...
Some(usize::from(offset) + row_value_offset)Proposed Changes
- Use checked arithmetic for matrix indexing:
let index = row_index
.checked_mul(suffix_count)
.and_then(|v| v.checked_add(column_index))?;
let Some(offset) = self.dense.get(index) else {
unreachable!(
"matrix index out of bounds: row={}, col={}, suffix_count={}",
row_index, column_index, suffix_count
);
};- Use checked arithmetic for final value calculation:
usize::from(offset).checked_add(row_value_offset)