Microsoft KB Archive/929020

= After you restore a sparse file on a Windows Server 2003-based computer that has antivirus software enabled, data is lost =

Article ID: 929020

Article Last Modified on 10/11/2007

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APPLIES TO


 * Microsoft Windows Server 2003, Standard Edition (32-bit x86)
 * Microsoft Windows Server 2003, Enterprise Edition
 * Microsoft Windows Server 2003, Datacenter Edition (32-bit x86)
 * Microsoft Windows Server 2003, Standard x64 Edition
 * Microsoft Windows Server 2003, Enterprise x64 Edition
 * Microsoft Windows Server 2003, Enterprise Edition for Itanium-based Systems
 * Microsoft Windows Server 2003, Datacenter Edition for Itanium-Based Systems

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SYMPTOMS
On a Microsoft Windows Server 2003-based computer, you can back up and restore a sparse file by using a backup program. However, if an antivirus program is running, a large sparse file may be damaged after you restore it.



CAUSE
A backup program closes the sparse file during the restore operation. Then, an antivirus program opens the sparse file as a section file to check whether it includes virus patterns. When the antivirus program calls the ZwCreateSection function, a timing issue occurs between the following operations:
 * The delayed write operation that is requested by the file close action
 * The flush cache operation that is requested by the antivirus program

In this scenario, the NTFS file system driver incorrectly sets the valid data length of the sparse file to a value that is smaller than the actual size of the file. Therefore, any attempt to read the data that is beyond the incorrect valid data length returns all zeros.



Hotfix information
A supported hotfix is now available from Microsoft. However, it is intended to correct only the problem that is described in this article. Apply it only to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next Windows Server 2003 service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Customer Support Services to obtain the hotfix. For a complete list of Microsoft Customer Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

Prerequisites
To apply this hotfix, you must have Windows Server 2003 Service Pack 1 (SP1) or Windows Server 2003 Service Pack 2 (SP2) installed. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

889100 How to obtain the latest service pack for Windows Server 2003

Restart requirement
You must restart the computer after you apply this hotfix.

Hotfix replacement information
This hotfix does not replace any other hotfixes.

File information
The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.

Windows Server 2003 with SP1, Itanium-based versions


WORKAROUND
To work around this problem, configure the antivirus program to exclude the sparse files when the program scans for viruses.



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section.



MORE INFORMATION
For more information about the terms that are used to describe software updates, click the following article number to view the article in the Microsoft Knowledge Base:

824684 Description of the standard terminology that is used to describe Microsoft software updates

Additional query words: data lost ValidDataLength

Keywords: kbbug kbfix kbqfe kbpubtypekc kbexpertiseinter kbhotfixserver kbwinserv2003postsp2fix KB929020

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