Issue creating directories in a VHD volume

Issue creating directories in a VHD volume

[David Lee]

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Hi,

I found some issues while trying to create directories to a volume on
a virtual disk (VHD).

-- SETUP --

* Windows 7 SP1 x64
* Cygwin 2.5.2 x86 installed and run under C:\Cygwin
* 100 MB Virtual Disk on D:\Test.vhd
* VHD has a 100 MB simple volume formatted as NTFS

* Tests were done under an account the joined the Local Administrators group.

-- TEST 1 --

1. I used Disk Management Console (diskmgmt.msc) to:
    a. Attach the VHD using Disk Management Console (GUI) (diskmgmt.msc).
    b. Mount the volume under C:\Cygwin\tmp\mount (Cygwin saw it as /tmp/mount).

2. Then I tried to create a directory in /tmp/mount inside bash:

   mkdir /tmp/mount/12345

3. Result: success (note: elevation was not needed).


-- TEST 2 --

Same procedure but used the diskpart.exe console utility instead.

1. It fired up a UAC prompt and I accepted it.

2. I created another directory: mkdir /tmp/mount/67890.

3. Result: success (note: although diskpart.exe was elevated, the bash
prompt itself wasn't.)


-- TEST 3 --

I wrote a simple utility in C/C++ to attach the VHD (using Win32 API
such as OpenVirtualDisk() and AttachVirtualDIsk()).

Source was attached with this message (demo.c)

1. I fired up an *elevated* Command Prompt.
2. Ran the utility to attach the DISK. Result: success.
3. Mounted the volume under C:\Cygwin\tmp\mount, either diskmgmt.msc
or diskpart.exe
4. Inside a bash prompt (no elevation), typed mkdir /tmp/mount/abcde
5. Result: permission denied (no directory was created).

6. In a Command Prompt (no elevation), the following SUCCEED:

   mkdir C:\Cygwin\tmp\mount\abcde

Any help is appreciated on why I got the 'permission denied' message.

David Lee.

[-- Attachment #2: demo.c --]
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/*
 * rename to demo.c and compile under cygwin as
 *
 * i686-w64-mingw32-gcc demo.c -lVirtDisk
 */

#define _WIN32_WINNT 0x601
#define INITGUID

#include <Windows.h>
#include <VirtDisk.h>
#include <tchar.h>
#include <stdio.h>

#define VHDPATH L"D:\\test.vhd"

int
main (void)
{
	VIRTUAL_STORAGE_TYPE vst;
	HANDLE hVhd;
	ATTACH_VIRTUAL_DISK_PARAMETERS params;
	DWORD rc;

	vst.DeviceId = VIRTUAL_STORAGE_TYPE_DEVICE_VHD;
	vst.VendorId = VIRTUAL_STORAGE_TYPE_VENDOR_MICROSOFT;

	rc = OpenVirtualDisk (
		&vst,
		VHDPATH,
		(VIRTUAL_DISK_ACCESS_MASK) (VIRTUAL_DISK_ACCESS_ATTACH_RW | VIRTUAL_DISK_ACCESS_DETACH),
		OPEN_VIRTUAL_DISK_FLAG_NONE,
		NULL,
		&hVhd
	);

	if (rc != ERROR_SUCCESS)
	{
		fwprintf (stderr, L"OpenVirtualDisk() failed, rc = %lu\n", rc);
		return 10;
	}

	params.Version = ATTACH_VIRTUAL_DISK_VERSION_1;

	rc = AttachVirtualDisk (
		hVhd,
		NULL,
		(ATTACH_VIRTUAL_DISK_FLAG)(ATTACH_VIRTUAL_DISK_FLAG_NO_DRIVE_LETTER | ATTACH_VIRTUAL_DISK_FLAG_PERMANENT_LIFETIME),
		0,
		&params,
		NULL
	);

	if (rc != ERROR_SUCCESS)
	{
		fwprintf (stderr, L"AttachVirtualDisk() failed, rc = %lu\n", rc);
		return 10;
	}

	wprintf (L"OK!\n");
	return 0;
}

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