Merge "Fix an error when overflows occur."

static constexpr size_t kPageSize = 4096;

static constexpr uint64_t AlignToPage(uint64_t address) {

  return (address + kPageSize - 1) & ~(kPageSize - 1);

static inline bool AlignToPage(uint64_t address, uint64_t* aligned_address) {

  if (__builtin_add_overflow(address, kPageSize - 1, aligned_address)) {

    return false;

  }

  *aligned_address &= ~(kPageSize - 1);

  return true;

}

std::unique_ptr<Maps> GetMaps(FuzzedDataProvider* data_provider) {

  std::map<uint64_t, uint64_t> map_ends;

  uint8_t entry_count = data_provider->ConsumeIntegralInRange<uint8_t>(0, kMaxMapEntryCount);

  for (uint8_t i = 0; i < entry_count; i++) {

    uint64_t start = AlignToPage(data_provider->ConsumeIntegral<uint64_t>());

    uint64_t end = AlignToPage(data_provider->ConsumeIntegralInRange<uint64_t>(start, UINT64_MAX));

    uint64_t start;

    if (!AlignToPage(data_provider->ConsumeIntegral<uint64_t>(), &start)) {

      // Overflowed.

      continue;

    }

    uint64_t end;

    if (!AlignToPage(data_provider->ConsumeIntegralInRange<uint64_t>(start, UINT64_MAX), &end)) {

      // Overflowed.

      continue;

    }

    if (start == end) {

      // It's impossible to see start == end in the real world, so

      // make sure the map contains at least one page of data.

    }

    map_ends[end] = start;

    uint64_t offset = AlignToPage(data_provider->ConsumeIntegral<uint64_t>());

    uint64_t offset;

    if (!AlignToPage(data_provider->ConsumeIntegral<uint64_t>(), &offset)) {

      // Overflowed.

      continue;

    }

    std::string map_info_name = data_provider->ConsumeRandomLengthString(kMaxMapInfoNameLen);

    uint8_t flags = PROT_READ | PROT_WRITE;