Symptoms

Consider the following scenario:

  • You share a file on a computer that is running Windows 7 or Windows Server 2008 R2.

  • Multiple users open the file by using the Server Message Block (SMB) Version 2 protocol from multiple remote computers.

  • One of the users updates the file.

In this scenario, data corruption may occur.

Note By default, the SMB Version 2 protocol is enabled in the following operating systems:

  • Windows 7

  • Windows Server 2008 R2

  • Windows Vista

  • Windows Server 2008


Cause

This issue occurs because the SMB redirector (Mrxsmb20.sys) incorrectly reports the position of the end of the file. Therefore, an application may unknowingly request to write to an incorrect location and cause the file to be corrupted.

Resolution

Hotfix information

A supported hotfix is 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 the problem described in this article. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if 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. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=supportNote The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

Prerequisites

To apply this hotfix, you must be running one of the following operating systems:

  • Windows 7

  • Windows 7 Service Pack 1 (SP1)

  • Windows Server 2008 R2

  • Windows Server 2008 R2 Service Pack 1 (SP1)

For more information about how to obtain a Windows 7 or Windows Server 2008 R2 service pack, click the following article number to view the article in the Microsoft Knowledge Base:

976932 Information about Service Pack 1 for Windows 7 and for Windows Server 2008 R2

Registry information

To use the hotfix in this package, you do not have to make any changes to the registry.

Restart requirement

You must restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace a previously released hotfix.

File information

The global version of this hotfix installs files that have the attributes that are listed in the following tables. The dates and the times for these files are listed in Coordinated Universal Time (UTC). The dates and the times for these files on your local computer are displayed in your local time together with your current daylight saving time (DST) bias. Additionally, the dates and the times may change when you perform certain operations on the files.

Windows 7 and Windows Server 2008 R2 file information notes


Important Windows 7 hotfixes and Windows Server 2008 R2 hotfixes are included in the same packages. However, hotfixes on the Hotfix Request page are listed under both operating systems. To request the hotfix package that applies to one or both operating systems, select the hotfix that is listed under "Windows 7/Windows Server 2008 R2" on the page. Always refer to the "Applies To" section in articles to determine the actual operating system that each hotfix applies to.

  • The files that apply to a specific product, SR_Level (RTM, SPn), and service branch (LDR, GDR) can be identified by examining the file version numbers as shown in the following table.

    Version

    Product

    SR_Level

    Service branch

    6.1.760
    0.
    21xxx

    Windows 7 and Windows Server 2008 R2

    RTM

    LDR

    6.1.760
    1.
    21xxx

    Windows 7 and Windows Server 2008 R2

    SP1

    LDR

  • The MANIFEST files (.manifest) and the MUM files (.mum) that are installed for each environment are listed separately in the "Additional file information for Windows Server 2008 R2 and for Windows 7" section. MUM and MANIFEST files, and the associated security catalog (.cat) files, are extremely important to maintain the state of the updated components. The security catalog files, for which the attributes are not listed, are signed with a Microsoft digital signature.

For all supported x86-based versions of Windows 7

File name

File version

File size

Date

Time

Platform

Mrxsmb20.sys

6.1.7600.21057

97,280

17-Sep-2011

22:39

x86

Mrxsmb20.sys

6.1.7601.21822

96,768

17-Sep-2011

23:50

x86

For all supported x64-based versions of Windows 7 and of Windows Server 2008 R2

File name

File version

File size

Date

Time

Platform

Mrxsmb20.sys

6.1.7600.21057

128,512

17-Sep-2011

22:58

x64

Mrxsmb20.sys

6.1.7601.21822

128,000

17-Sep-2011

23:49

x64

For all supported IA-64–based versions of Windows Server 2008 R2

File name

File version

File size

Date

Time

Platform

Mrxsmb20.sys

6.1.7600.21057

313,344

17-Sep-2011

22:20

IA-64

Mrxsmb20.sys

6.1.7601.21822

310,784

17-Sep-2011

22:18

IA-64

Status

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

More Information

For more information about software update terminology, 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

For more information about a similar issue, click the following article number to view the article in the Microsoft Knowledge Base:

2028965 Data corruption when multiple users perform read and write operations to a shared file in the SMB2 environment

Additional file information

Additional file information for Windows 7 and for Windows Server 2008 R2

Additional files for all supported x86-based versions of Windows 7

File name

Update.mum

File version

Not applicable

File size

2,773

Date (UTC)

18-Sep-2011

Time (UTC)

07:45

Platform

Not applicable

File name

X86_5580f8cdd662ece1f532e40f7b175465_31bf3856ad364e35_6.1.7601.21822_none_4b2d9c6fe908c864.manifest

File version

Not applicable

File size

701

Date (UTC)

18-Sep-2011

Time (UTC)

07:45

Platform

Not applicable

File name

X86_5ab6c295a7a9824b9fdfa31b040e15cb_31bf3856ad364e35_6.1.7600.21057_none_50c708effdb04d19.manifest

File version

Not applicable

File size

701

Date (UTC)

18-Sep-2011

Time (UTC)

07:45

Platform

Not applicable

File name

X86_microsoft-windows-smb20-minirdr_31bf3856ad364e35_6.1.7600.21057_none_8b5d3a82041d1a11.manifest

File version

Not applicable

File size

4,035

Date (UTC)

18-Sep-2011

Time (UTC)

01:36

Platform

Not applicable

File name

X86_microsoft-windows-smb20-minirdr_31bf3856ad364e35_6.1.7601.21822_none_8d5f2f9e012f7d5c.manifest

File version

Not applicable

File size

4,035

Date (UTC)

18-Sep-2011

Time (UTC)

03:15

Platform

Not applicable

Additional files for all supported x64-based versions of Windows 7 and of Windows Server 2008 R2

File name

Amd64_5f3240e27a970e5e8fb97cbfd1bf0419_31bf3856ad364e35_6.1.7600.21057_none_e95b60bbea8b7db8.manifest

File version

Not applicable

File size

705

Date (UTC)

18-Sep-2011

Time (UTC)

07:45

Platform

Not applicable

File name

Amd64_eea11ce079e9dda4bc2adaff089dbe57_31bf3856ad364e35_6.1.7601.21822_none_5cfb22d6211ab548.manifest

File version

Not applicable

File size

705

Date (UTC)

18-Sep-2011

Time (UTC)

07:45

Platform

Not applicable

File name

Amd64_microsoft-windows-smb20-minirdr_31bf3856ad364e35_6.1.7600.21057_none_e77bd605bc7a8b47.manifest

File version

Not applicable

File size

4,039

Date (UTC)

18-Sep-2011

Time (UTC)

02:18

Platform

Not applicable

File name

Amd64_microsoft-windows-smb20-minirdr_31bf3856ad364e35_6.1.7601.21822_none_e97dcb21b98cee92.manifest

File version

Not applicable

File size

4,039

Date (UTC)

18-Sep-2011

Time (UTC)

04:27

Platform

Not applicable

File name

Update.mum

File version

Not applicable

File size

3,215

Date (UTC)

18-Sep-2011

Time (UTC)

07:45

Platform

Not applicable

Additional files for all supported IA-64–based versions of Windows Server 2008 R2

File name

Ia64_0c1639807add3edf1563af25e3f262d8_31bf3856ad364e35_6.1.7601.21822_none_8bc599fc49590fa2.manifest

File version

Not applicable

File size

703

Date (UTC)

18-Sep-2011

Time (UTC)

07:45

Platform

Not applicable

File name

Ia64_25d2bac3af5b2a31f1b4a542796d7f5a_31bf3856ad364e35_6.1.7600.21057_none_9044fcafeb13bf3b.manifest

File version

Not applicable

File size

703

Date (UTC)

18-Sep-2011

Time (UTC)

07:45

Platform

Not applicable

File name

Ia64_microsoft-windows-smb20-minirdr_31bf3856ad364e35_6.1.7600.21057_none_8b5ede78041b230d.manifest

File version

Not applicable

File size

4,037

Date (UTC)

18-Sep-2011

Time (UTC)

02:24

Platform

Not applicable

File name

Ia64_microsoft-windows-smb20-minirdr_31bf3856ad364e35_6.1.7601.21822_none_8d60d394012d8658.manifest

File version

Not applicable

File size

4,037

Date (UTC)

18-Sep-2011

Time (UTC)

04:04

Platform

Not applicable

File name

Update.mum

File version

Not applicable

File size

2,168

Date (UTC)

18-Sep-2011

Time (UTC)

07:45

Platform

Not applicable

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