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Commit d00b7d1f authored by Andy Hung's avatar Andy Hung Committed by Lajos Molnar
Browse files

Add isSafeArraySize for new array size checks

Bug: 15328708
Change-Id: I9dfca30745c3e4dda91c3894363462f8631c41a1
parent 141670d4
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+27 −0
Original line number Diff line number Diff line
@@ -22,4 +22,31 @@
    name(const name &); \
    name &operator=(const name &)

/* Returns true if the size parameter is safe for new array allocation (32-bit)
 *
 * Example usage:
 *
 * if (!isSafeArraySize<uint32_t>(arraySize)) {
 *     return BAD_VALUE;
 * }
 * ...
 * uint32_t *myArray = new uint32_t[arraySize];
 *
 * There is a bug in gcc versions earlier than 4.8 where the new[] array allocation
 * will overflow in the internal 32 bit heap allocation, resulting in an
 * underallocated array. This is a security issue that allows potential overwriting
 * of other heap data.
 *
 * An alternative to checking is to create a safe new array template function which
 * either throws a std::bad_alloc exception or returns NULL/nullptr_t; NULL considered
 * safe since normal access of NULL throws an exception.
 *
 * https://securityblog.redhat.com/2012/10/31/array-allocation-in-cxx/
 */
template <typename T, typename S>
bool isSafeArraySize(S size) {
    return size >= 0                            // in case S is signed, ignored if not.
            && size <= 0xffffffff / sizeof(T);  // max-unsigned-32-bit-int / element-size.
}

#endif  // A_BASE_H_