Question: Take a simple heap corruption example in C/C++
Answer:
Heap corruption can occur from various reasons such as double free (freeing a pointer twice), old pointer reuse (reusing a pointer after freed), buffer overrun (writing beyond buffer's boundary).
The following code will raise heap corruption because of double free.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | // heap corruption due to double free#include <iostream>char* mem = NULL;int main(int argc, char* argv[]){ mem = (char*)malloc(10 * sizeof(char)); mem[0] = 'A'; free(mem); free(mem); // double free}</iostream> |
When running the debug build in WinDbg,
"Invalid address specified to RtlValidateHeap" error will be thrown as first chance exception.
0:000> g HEAP[heaptest.exe]: Invalid address specified to RtlValidateHeap( 009E0000, 009F4808 ) (3a60.3d78): Break instruction exception - code 80000003 (first chance) eax=00779000 ebx=009f4800 ecx=009e4d44 edx=0098f431 esi=009e0000 edi=009e0000 eip=77728c59 esp=0098f598 ebp=0098f5a4 iopl=0 nv up ei pl nz na po nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00000202 ntdll!RtlpValidateHeapEntry+0x61d14: 77728c59 cc int 3 0:000> g Debug Assertion Failed! Program: C:\src\heaptest\Debug\heaptest.exe File: minkernel\crts\ucrt\src\appcrt\heap\debug_heap.cpp Line: 904 Expression: _CrtIsValidHeapPointer(block) ...