This commit addresses several integer overflow and underflow security issues:

1. osquery/tables/system/darwin/smc_keys.cpp:

   • Added overflow checks in strtoul() to prevent shift overflow when size > 4
   • Added overflow checks in strtoull() to prevent shift overflow when size > 8
   • Changed shift operation from '1 << fractionalBits' to '1U << fractionalBits' to use unsigned arithmetic and prevent undefined behavior

2. osquery/utils/conversions/windows/strings.cpp:

   • Added overflow checks before 'str.length() * 2' and 'str.length() * 4' multiplications to prevent integer overflow during string conversion

3. osquery/filesystem/linux/mem.cpp:

   • Added overflow check for 'offset + length' calculation before mmap() to prevent integer overflow in memory mapping operations

4. osquery/tables/system/posix/smbios_utils.cpp:

   • Changed offset parameter type from uint8_t to size_t in dmiToWord(), dmiToDWord(), dmiToQWord(), and dmiWordToHexStr() functions to prevent uint8_t wraparound when adding offset values (1, 3, 7)

5. osquery/tables/system/windows/prefetch.cpp:

   • Added underflow checks before 'size - total_length' and 'volume_size - dir_offset' subtractions
   • Added overflow checks before '(length + 1) * sizeof(WCHAR)' multiplications to prevent integer overflow in prefetch parsing

These fixes prevent potential security vulnerabilities related to integer arithmetic that could lead to buffer overflows, incorrect memory access, or other undefined behavior.

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