Is it possible for a child process to read a file which is locked by parent process?-CodePudding

I have a Parent process which creates a file using CreateFile() and locks it. below is the code:

m_hWriterLockFile = ::CreateFile("C:\\Test.txt", 
                             GENERIC_READ | GENERIC_WRITE, 
                             0, // exclusive
                             NULL, // default security
                             OPEN_ALWAYS,
                             FILE_ATTRIBUTE_NORMAL,
                             NULL);

Now, I want only the child process to access this locked file. I do not want any other process to read this file.

I have created a child process. Below is the sample code:

// Initialize a security attributes structure.
SECURITY_ATTRIBUTES sa;
sa.nLength = sizeof(SECURITY_ATTRIBUTES);
sa.lpSecurityDescriptor = pSD;
sa.bInheritHandle = TRUE;
    if (!CreateProcess("FileReader.exe", // I want to invoke this exe
    "C:\\Test.txt",
    &sa,
    NULL,
    TRUE,
    0,
    NULL,
    NULL,
    &si,
    &pi))
{
    std::cout << "Create Process Faild (%d) " << GetLastError() << '\n';
}

Unfortunately, I am not able to achieve my goal, is there anyone who can help me? Is there any other way to achieve this? I will share more information(code) if needed.

Note: I didn't share the complete code to make the post shorter.

CodePudding user response：

Here is the answer of of my question :

create the file with an inheritable handle and pass that handle to the child process. A simple way to do this is to pass it as a command line parameter. We must pass a SECURITY_ATTRIBUTES structure that specifies TRUE for bInheritHandle to CreateFile and also pass TRUE to the bInheritHandles parameter of the call to CreateProcess.

Create File

Ex:

    SECURITY_ATTRIBUTES sa{ sizeof sa, nullptr, TRUE };
HANDLE hFile = CreateFileA("C:\\Test.txt",
    GENERIC_READ | GENERIC_WRITE,
    0,
    &sa,
    CREATE_ALWAYS,
    FILE_ATTRIBUTE_NORMAL,
    NULL);

Child Process:

UINT_PTR uiHandle = reinterpret_cast<UINT_PTR>(hFile);

        sprintf_s(szCmdLine, "\"%s\" %Iu", szExePath, uiHandle);

        if (CreateProcessA(nullptr,
            szCmdLine,
            nullptr,
            nullptr,
            TRUE,
            CREATE_NEW_CONSOLE,
            nullptr,
            nullptr,
            &si,
            &pi))
        {
           CloseHandle(pi.hThread);
           CloseHandle(pi.hProcess);

        }