[C] Windows 10 code injection in anderen Prozess

#include <windows.h>
#include <psapi.h>

#define PROCESS_ID_FOR_INJECTION 2832

struct inj_data
{
    HMODULE WINAPI (*load_library) (LPCSTR lpFileName);
    FARPROC WINAPI (*get_proc_address) (HMODULE hModule, LPVOID lpProcName);
    HMODULE kernelDll;
    char message_box_name[10];
    char message_box_string1[10];
};

static DWORD WINAPI thread_main(struct inj_data *injData)
{
    int WINAPI (*message_box) (HWND, LPCTSTR, LPCTSTR, UINT);
    message_box = injData->get_proc_address(injData->kernelDll,
                                            injData->message_box_name);
    (*message_box)(NULL,
                   injData->message_box_string1,
                   injData->message_box_string1,
                   MB_OKCANCEL);
}
    

int main(void)
{
    HANDLE proc, newThread;
    struct inj_data *injData;
    HMODULE kernelDll;
    LPVOID injDataBase, injFuncBase;

    if (!(proc = OpenProcess(PROCESS_CREATE_THREAD | PROCESS_QUERY_INFORMATION
                          | PROCESS_VM_OPERATION | PROCESS_VM_WRITE 
                          | PROCESS_VM_READ,
                          FALSE,
                          PROCESS_ID_FOR_INJECTION)))
    {
        return 1;
    }

    injData = malloc(sizeof (struct inj_data));
    #define MESSAGEBOX "MessageBox"
    memcpy(injData->message_box_name, MESSAGEBOX, strlen(MESSAGEBOX));
    #define STRING1 "Hello"
    memcpy(injData->message_box_string1, STRING1, strlen(STRING1)); 
    kernelDll = LoadLibrary("kernel32.dll");
    injData->kernelDll = kernelDll;
    injData->load_library = GetProcAddress(kernelDll, "LoadLibraryA");
    injData->get_proc_address = GetProcAddress(kernelDll, "GetProcAddressA");
    if (NULL == (injDataBase = VirtualAllocEx(proc,
                                              NULL,
                                              sizeof (struct inj_data),
                                              MEM_COMMIT,
                                              PAGE_READWRITE)))
    {
        return 2;
    }
    if (!WriteProcessMemory(proc,
                            injDataBase,
                            injData,
                            sizeof (injData),
                            NULL))
    {
        return 3;
    }
    if (NULL == (injFuncBase = VirtualAllocEx(proc,
                                              NULL,
                                              ((SIZE_T)(&main) - (SIZE_T)(&thread_main)),
                                              MEM_COMMIT,
                                              PAGE_READWRITE)))
    {
        return 4;
    }
    if (!WriteProcessMemory(proc,
                            injFuncBase,
                            &thread_main,
                            ((SIZE_T)&main - (SIZE_T)&thread_main),
                            NULL))
    {
        return 5;
    }
    if (NULL == (newThread = CreateRemoteThread(proc,
                                                 NULL,
                                                 0,
                                                 (LPTHREAD_START_ROUTINE)injFuncBase,
                                                 injDataBase,
                                                 NULL,
                                                 NULL)))
    {
        return 6;
    }
    return 0;
}