Microsoft KB Archive/325929

= A null session leak is caused by the GetFileAttributes function on Windows XP clients =

Article ID: 325929

Article Last Modified on 8/29/2007

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APPLIES TO


 * Microsoft Windows XP Home Edition
 * Microsoft Windows XP Home Edition
 * Microsoft Windows XP Professional
 * Microsoft Windows XP Professional
 * Microsoft Windows XP Professional x64 Edition

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This article was previously published under Q325929



SYMPTOMS
Microsoft Windows NT 4.0-based servers may show many null sessions when those servers are accessed by Windows XP-based clients. You can see the null sessions by typing net session at a command prompt on a Windows NT 4.0-based server.

Also, when you use Windows Explorer to delete a read-only file that is located on an IBM OS/2 Warp4-based server with the HPFS file system, the file may not be deleted and you do not receive any notification that the file-deletion process did not work. Note that this problem does not occur if you click to clear the Display delete confirmation dialog check box in the Recycle Bin Properties dialog box.

This problem may be triggered by services that are running in the Local System context on the Windows XP-based clients. The problem occurs if these services make calls to the GetFileAttributes Win32 function to obtain information about a share on a Windows NT 4.0-based server when the Windows XP-based client views the share in Windows Explorer.



CAUSE
When the null-sessions problem occurs, the Windows XP-based client combines a &quot;Session Setup And X&quot; Server Message Block (SMB) request and a &quot;Tree Connect and X&quot; SMB request into a single SMB request. If this combined request does not succeed, Windows XP does not test to determine which of the two requests did not succeed. Instead, Windows XP always assumes that the &quot;Session Setup And X&quot; request did not succeed, and that no cleanup is required.

If the &quot;Session Setup And X&quot; request succeeds but the &quot;Tree Connect And X&quot; request does not succeed (for example, when a service that is running under the Local System context tries to access a share on the Windows NT 4.0-based server), the client should send a logoff request to remove the session that was created by the &quot;Session Setup And X&quot; request.



Service pack information
To resolve this problem, obtain the latest service pack for Windows XP. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

322389 How to obtain the latest Windows XP service pack

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

To resolve this problem, submit a request to Microsoft Online Customer Services to obtain the hotfix. To submit an online request to obtain the hotfix, visit the following Microsoft Web site:

http://go.microsoft.com/?linkid=6294451

Note If additional issues occur or any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. To create a separate service request, visit the following Microsoft Web site:

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

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 tool in Control Panel.

Windows XP, 32-bit original release versions
  Date         Time   Version      Size     File name 16-Aug-2002 21:43  5.1.2600.56  391,936  Mrxsmb.sys

Windows XP with Service Pack 1 (SP1), 32-bit versions
  Date         Time   Version            Size    File name --  22-Sep-2002  04:04  5.1.2600.1123     392,576  Mrxsmb.sys

Windows XP Professional 64-Bit Edition (Itanium) with SP1
  Date         Time   Version            Size    File name --  22-Sep-2002  06:22  5.1.2600.1123   1,236,736  Mrxsmb.sys

This hotfix modifies Windows XP to send the two requests separately. Therefore, if the &quot;Session Setup And X&quot; request succeeds but the &quot;Tree Connect And X&quot; request does not succeed, a logoff request is sent to close the session that was created by the &quot;Session Setup And X&quot; request and to prevent the null-session leak.



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

This problem was first corrected in Windows XP Service Pack 2.

Additional query words: 331960

Keywords: kbhotfixserver kbqfe kbwinxppresp2fix kbwinxpsp2fix kbbug kbfix kbqfe KB325929

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