How do i solve this run time error?

Question

I tried to hook CreateThread() function by using Detour library. But it won't work due to some errors. Finally just call the CreateThread function rather than direct call, I construct my own DLL. During DLL construct and program compilation. It doesn't return any error.But, while running its getting stop.

testdll.cpp

---

#include <windows.h>

BOOL _stdcall DllMain( HANDLE hModule, DWORD  ul_reason_for_call, LPVOID lpReserved)
{
    return TRUE;
}

extern "C" _declspec(dllexport) bool _stdcall C_thread(LPSECURITY_ATTRIBUTES lpThreadAttributes,SIZE_T dwStackSize,LPTHREAD_START_ROUTINE lpStartAddress,LPVOID lpParameter,DWORD dwCreationFlags,LPDWORD lpThreadId)
{
    HANDLE hThread;
    DWORD threadID;
    hThread = CreateThread(lpThreadAttributes,dwStackSize,lpStartAddress,lpParameter,dwCreationFlags,lpThreadId);
    return hThread;
}

---

by using above testdll.cpp, I am constructing DLL.

cl /nologo /W3 /Ox /Zi /MD /LD test.cpp

link /DEBUG /SUBSYSTEM:WINDOWS /ENTRY:DllMain /OUT:testdll_temp.dll /DEF:test.def testdll_temp.obj kernel32.lib

testcall.cpp //* main program *//

---

#include<stdio.h>
#include<windows.h>

DWORD WINAPI ThreadFun(LPVOID param)
{
    printf("hi");
    return 0;
}

int main()
{
    HANDLE h;   
    DWORD threadID;
    typedef bool (_stdcall *CALL_A)(LPSECURITY_ATTRIBUTES lpThreadAttributes,SIZE_T dwStackSize,LPTHREAD_START_ROUTINE lpStartAddress,LPVOID lpParameter,DWORD dwCreationFlags,LPDWORD lpThreadId);
    printf("Creating Handle");
    HINSTANCE hinstDLL;
    BOOL fFreeDLL;

    printf("\nLoading library test.dll .... ");

    hinstDLL = LoadLibrary("testdll.dll");
    if (hinstDLL != NULL)
    {
        printf("\nLibrary loaded\n");
        CALL_A C_thread;
        C_thread = (CALL_A)GetProcAddress(hinstDLL,"C_thread"); 
        if (C_thread != NULL)
        {
            printf("lets see, it calling");
            HANDLE a = C_thread(NULL, 0, ThreadFu, NULL, 0, &threadID);
            printf("working");
        }
        else
        {
            printf("Address not found ");
        }
        fFreeDLL = FreeLibrary(hinstDLL);
    }    
    else
        printf("Library not found");
    return 0;
}

---

Even i compiled this, cl /Zi testcall.cpp

But I run testcall.exe file. Library was properly loaded, But while executing below line, It getting stop.

HANDLE a = C_thread(NULL, 0, ThreadFu, NULL, 0, &threadID);

I am using Visual-C++ command prompt (not GUI). Please help me to solve this. If anything, correct me.

Answer 1

Your program has undefined behavior. When you create a thread it is not guaranteed that it runs immediately. Even if it runs immediately you have a race condition between the FreeLibraryand the run-time call to printf in the thread.

Your main thread must wait until the secondary thread has terminated:

    CALL_A C_thread;
    C_thread = (CALL_A)GetProcAddress(hinstDLL,"C_thread"); 

    if (C_thread != NULL)
    {
        printf("lets see, it calling");
        HANDLE a = C_thread(NULL, 0, ThreadFu, NULL, 0, &threadID);
        printf("working");

        if (WaitForSingleObject(a, some_time_or_infinite) != WAIT_OBJECT_0)
        {
            // this is dirty since the thread has probable no chance to release resources.
            TerminateThread(hThread);
        }
    }
    else
    {
        printf("Address not found ");
    }

    fFreeDLL = FreeLibrary(hinstDLL);