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Q179433: Cache Manager May Cause Data Corruption on SMB Servers on FAT

Article: Q179433
Product(s): Microsoft Windows NT
Version(s): WinNT:4.0
Operating System(s): 
Keyword(s): kbWinNT400sp4fix
Last Modified: 10-AUG-2001

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The information in this article applies to:

- Microsoft Windows NT Workstation version 4.0 
- Microsoft Windows NT Server version 4.0 
- Microsoft Windows NT Server version 4.0, Terminal Server Edition 
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SYMPTOMS
========

You may encounter corrupted files if Windows NT is installed on a FAT partition
or shared CDFS volume that has a file system filter driver running on that
volume.

CAUSE
=====

This problem is caused by Memory Descriptor List (MDL) interactions between the
Cache Manager, the SMB server, the file system filter driver, and FAT. There is
an error in the Windows NT Cache Manager that may cause data corruption when the
following conditions are true:

- Windows NT file server (Srv.sys) is running and sharing data on a local
  FAT-based file system (Fastfat.sys).

  NOTE: This problem does not occur if the server is sharing data on NTFS
  systems. However, the problem may exist with other third-party file systems
  or other code that exercises MDL I/O in ways similar to Srv.sys.

- Windows NT is using a file system filter driver. The filter driver must be
  aware of the Fast MDL routines and it must filter I/O on the FAT-based file
  system.

  For more information on file system filter drivers, please see the following
  article in the Microsoft Knowledge Base:

  ARTICLE-ID: Q168513
  TITLE : Windows NT Installable File System Kit (IFS) Description

  NOTE: Windows NT 4.0 does not include any file system filter drivers.

For example, when a filter driver filters data I/O on an SMB server, which is
shared on a FAT file system, the I/O requests that flow from the network system
through the server, to the filter driver, and into the FAT partition may cause
data corruption.

RESOLUTION
==========

An updated version of the Windows NT kernel (which includes Cache Manager) no
longer ignores returns from the filter driver that indicate the filter did not
write the data or free the MDL. Cache Manager now takes system- defined default
actions.

To resolve this problem, obtain the latest service pack for Windows NT 4.0 or
Windows NT Server 4.0, Terminal Server Edition. For additional information,
please see the following article in the Microsoft Knowledge Base:

  Q152734 How to Obtain the Latest Windows NT 4.0 Service Pack


For your convenience, the English version of this post-SP3 hotfix has been posted
to the following Internet location. However, Microsoft recommends that you
install Windows NT 4.0 Service Pack 4 to correct this problem.

  ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/usa/NT40/hotfixes-postSP3/getadmin-fix

NOTE: Service Pack 3 must be applied to Windows NT 4.0 prior to applying this
fix.

Mdl-fix has been superseded by Getadmin-fix. You can find the original hotfix at
the following Microsoft ftp site:

  ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/usa/NT40/hotfixes-postSP3/archive/mdl-fix

You can work around this problem by using NTFS partitions for SMB server-based
shares instead of FAT partitions or by not using any file system filter drivers
that filter I/O on top of FAT-based server volumes.

STATUS
======

Microsoft has confirmed this to be a problem in Windows NT 4.0 and Windows NT
Server 4.0, Terminal Server Edition. This problem was first corrected in Windows
NT 4.0 Service Pack 4.0 and Windows NT Server 4.0, Terminal Server Edition
Service Pack 4.


Additional query words: CcMdlWriteComplete IRP_MN_MDL_COMPLETE IFS Kit NO_MORE_SYSTEM_PTES
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Keywords          : kbWinNT400sp4fix 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400 kbNTTermServ400 kbNTTermServSearch
Version           : WinNT:4.0
Issue type        : kbbug
Solution Type     : kbfix

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