Fix for CWE-190: Integer Overflow or Wraparound

[ekse]

🐕 Corgea issued a PR to fix a vulnerability found in lib/libwasm.c.

It is CWE-190: Integer Overflow or Wraparound that has a severity of 🔴 High.

🪄 Fix explanation

The fix prevents integer overflow when calculating memory allocation size by casting to "size_t" and validating that adding 1 doesn’t wrap around, ensuring safe allocation and mitigating overflow-related vulnerabilities.
- Cast "field_len" to "size_t" before adding 1 to avoid overflow in pointer-size arithmetic: "size_t alloc_size = (size_t) field_len + 1;".
- Verify no wraparound by checking "alloc_size <= field_len"; if true, jump to error handling to prevent unsafe allocation.
- Replace original allocation with "calloc(1, alloc_size)", ensuring correct memory size is requested.
- Add a null check for the allocation result, jumping to "parse_error" if allocation fails, improving robustness.

💡 Important Instructions

Ensure that parse_error handles cleanup correctly to prevent memory leaks or undefined behavior after this early exit.

See the issue and fix in Corgea.