1 /* 2 * Copyright (C) 2010 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef A_BASE_H_ 18 19 #define A_BASE_H_ 20 21 #define ARRAY_SIZE(a) (sizeof(a) / sizeof(*(a))) 22 23 #define DISALLOW_EVIL_CONSTRUCTORS(name) \ 24 name(const name &); \ 25 name &operator=(const name &) 26 27 /* Returns true if the size parameter is safe for new array allocation (32-bit) 28 * 29 * Example usage: 30 * 31 * if (!isSafeArraySize<uint32_t>(arraySize)) { 32 * return BAD_VALUE; 33 * } 34 * ... 35 * uint32_t *myArray = new uint32_t[arraySize]; 36 * 37 * There is a bug in gcc versions earlier than 4.8 where the new[] array allocation 38 * will overflow in the internal 32 bit heap allocation, resulting in an 39 * underallocated array. This is a security issue that allows potential overwriting 40 * of other heap data. 41 * 42 * An alternative to checking is to create a safe new array template function which 43 * either throws a std::bad_alloc exception or returns NULL/nullptr_t; NULL considered 44 * safe since normal access of NULL throws an exception. 45 * 46 * https://securityblog.redhat.com/2012/10/31/array-allocation-in-cxx/ 47 */ 48 template <typename T, typename S> 49 bool isSafeArraySize(S size) { 50 return size >= 0 // in case S is signed, ignored if not. 51 && size <= 0xffffffff / sizeof(T); // max-unsigned-32-bit-int / element-size. 52 } 53 54 #endif // A_BASE_H_ 55
