System Error 0x5: CreateFileMapping()

Question

I wish to implement IPC using Named Shared Memory.

To do this, one of the steps is getting a handle to a Mapping Memory Object, using CreateFileMapping().

I do it exactly as MSDN website reccommends: http://msdn.microsoft.com/en-us/library/aa366551(v=VS.85).aspx:

hFileMappingHandle = CreateFileMapping
    (
        INVALID_HANDLE_VALUE,      // use paging file
        NULL,                      // default security 
        PAGE_READWRITE,            // read/write access
        0,            // maximum object size (high-order DWORD) 
        256,            // maximum object size (low-order DWORD)  
        "Global\\MyFileMappingObject"          // name of mapping object
    ); 
DWORD dwError = GetLastError();

However, the handle returned is always 0x0, and the System Error Code returned is: 0x5 (Access Denied.)

• Only Named Memory Sharing desired (not file sharing).
• Windows 7 x64 bit OS
• Administrator's user rights available
• Developed Application: 64bit Plug-In application (.dll)

Does anybody have the same experience, and a way to fix it, please? I use MSDN site as my reference, so I to not think, there is problem in the code.

Answer 1

Looks like you don't have enough privileges.

From MSDN:

Creating a file mapping object in the global namespace from a session other than session zero requires the SeCreateGlobalPrivilege privilege. For more information, see Kernel Object Namespaces.

...

The creation of a file-mapping object in the global namespace, by using CreateFileMapping, from a session other than session zero is a privileged operation. Because of this, an application running in an arbitrary Remote Desktop Session Host (RD Session Host) server session must have SeCreateGlobalPrivilege enabled in order to create a file-mapping object in the global namespace successfully. The privilege check is limited to the creation of file-mapping objects, and does not apply to opening existing ones. For example, if a service or the system creates a file-mapping object, any process running in any session can access that file-mapping object provided that the user has the necessary access.

Answer 2

Administrators, Services and Network Services have SeCreateGlobalPrivilege by default. You must remember though, that Windows7/Vista does not run everything as admin. So use "Start as administrator" to make "Global\" work for your application. If you're debugging, start Visual Studio as admin also.

Answer 3

To create global file mappings you need the SeCreateGlobalPrivilege privilege - do you have that? Access-denied implies this is a permissions problem, for sure.