[2005] Win32 API Error: "Attempted to read or write protected memory."

Hey Guys,

Trying to play with the Win32 API but am getting the following error:

"Attempted to read or write protected memory. This is often an indication that other memory is corrupt." {System.AccessViolationException}

This occurs during a call to CreateFile():

VB Code:

sFullDrivePath = "\\.\" & sDriveLetter & ":"
 
hDevice = CreateFile(sFullDrivePath, GENERIC_READ, FILE_SHARE_READ Or FILE_SHARE_WRITE, vbNull, OPEN_EXISTING, 0, 0)

I am attempting to open a USB disk but when I call CreateFile() to get my handle it fails...

I am on a machine that is part of a domain, I am a local admin but not domain admin. Therefore I should have enough rights to perform this operation? You only need full admin to open a hard disk.

Any ideas?
Thanks,
Matt.

I assume this has to be a security issue with the framework.

I am making an unmanaged call but the error I am receiving is caught by the managed code.

How can I tell the framework to back off its security?

Matt.

It is quite likely to be an error in your API declaration.
Can you post that?

Also - vbNull is not a .NET friendly thing at all.

Hey Merrion,

You got it! But didn't....

I simply changed the vbNull to 0 and BOOM, my device handle is returned!

So I was very happy for a second until I then tried to move the file pointer using SetFilePointer() and got the same error!

VB Code:

<DllImport("kernel32.dll")> _
    Public Function SetFilePointer( _
        ByVal hFile As Long, _
        ByVal lDistanceToMove As Long, _
        ByVal lpDistanceToMoveHigh As Long, _
        ByVal dwMoveMethod As Long) As Long
    End Function
 
    Public Const FILE_BEGIN As Long = 0
    Public Const FILE_EOF As Long = &HFFFFFFFF

Used like so:

VB Code:

If SetFilePointer(hDevice, (iSectorSize * iSectorNumber), 0, FILE_BEGIN) = FILE_EOF Then
   MessageBox.Show("Unable to find sector " & iSectorNumber, "Error!", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
   Return baDataBuffer
End If

This threw the same "Attempted to read or write....." error. Hmmmmmm

Thanks Merrion,
Matt.

OK - with the api declaration we can see a problem.

In .NET an integer is 32 bits so replace Long with Integer:-

VB Code:

<DllImport("kernel32.dll")> _
    Public Function SetFilePointer( _
        ByVal hFile As Int32 , _
        ByVal lDistanceToMove As int32, _
        ByVal lpDistanceToMoveHigh As Int32, _
        ByVal dwMoveMethod As Int32) As Int32
    End Function
 
    Public Const FILE_BEGIN As Int32 = 0
    Public Const FILE_EOF As int32 = &HFFFFFFFF