Symptoms

Consider the following scenario:

  • You run a 32-bit application on a computer that is running a 64-bit version of Windows 7 or of Windows Server 2008 R2.

  • An exception occurs when the direction flag is set to 1.

    Note The direction flag should still be 0 inside the exception handler.

  • The exception handler thread enters an alterable wait state, and an asynchronous procedure call (APC) occurs during the alterable wait.

In this scenario, the direction flag is incorrectly set to 1 after the alterable wait is finished. Therefore, all operations that rely on the direction flag bit write to a wrong location or read from the wrong data.

Cause

This issue occurs because the EFLAGS direction bit is restored after the APC. However, the related WOW64 function does not save or restore the EFLAGS direction bit. Instead, the function uses the data that is stored before the exception occurs. Therefore, the EFLAGS direction bit is set incorrectly after the APC.

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 Windows 7 or 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 may have to restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace a previously released hotfix.

File information

The English (United States) 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 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 x64-based versions of Windows 7 and of Windows Server 2008 R2

File name

File version

File size

Date

Time

Platform

Ntvdm64.dll

6.1.7600.16385

16,384

14-Jul-2009

01:41

x64

Wow64.dll

6.1.7600.20737

243,200

18-Jun-2010

09:42

x64

Wow64cpu.dll

6.1.7600.20737

13,312

18-Jun-2010

09:42

x64

Wow64win.dll

6.1.7600.16385

361,984

14-Jul-2009

01:41

x64

Acwow64.dll

6.1.7600.20737

44,032

18-Jun-2010

09:06

x86

Instnm.exe

6.1.7600.20737

7,680

18-Jun-2010

06:44

x86

Ntvdm64.dll

6.1.7600.20737

14,336

18-Jun-2010

09:08

x86

Setup16.exe

3.1.0.1918

25,600

18-Jun-2010

09:06

x86

User.exe

6.1.7600.20737

2,048

18-Jun-2010

06:44

x86

Wow32.dll

6.1.7600.20737

5,120

18-Jun-2010

09:04

x86

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

File name

File version

File size

Date

Time

Platform

Ia32exec.bin

6.8.6808.0

8,781,824

10-Jun-2009

21:15

Not Applicable

Ntvdm64.dll

6.1.7600.16385

27,648

14-Jul-2009

01:48

IA-64

Wow64.dll

6.1.7600.20737

580,608

18-Jun-2010

08:44

IA-64

Wow64cpu.dll

6.1.7600.20737

36,864

18-Jun-2010

08:44

IA-64

Wow64win.dll

6.1.7600.16385

716,288

14-Jul-2009

01:50

IA-64

Wowia32x.dll

6.8.6807.0

88,576

18-Jun-2010

08:44

IA-64

Acwow64.dll

6.1.7600.20737

44,032

18-Jun-2010

09:06

x86

Instnm.exe

6.1.7600.20737

7,680

18-Jun-2010

06:44

x86

Ntvdm64.dll

6.1.7600.20737

14,336

18-Jun-2010

09:08

x86

Setup16.exe

3.1.0.1918

25,600

18-Jun-2010

09:06

x86

User.exe

6.1.7600.20737

2,048

18-Jun-2010

06:44

x86

Wow32.dll

6.1.7600.20737

5,120

18-Jun-2010

09:04

x86

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 the direction flag, visit the following Microsoft website:

General information about the direction flagFor more information about APCs, visit the following Microsoft website:

General information about the APCsFor 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

Additional file information

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

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

File name

Amd64_42e64950aa8c344092efd47996c9100b_31bf3856ad364e35_6.1.7600.20737_none_5efa25eb1e178b03.manifest

File version

Not Applicable

File size

697

Date (UTC)

18-Jun-2010

Time (UTC)

14:19

Platform

Not Applicable

File name

Amd64_43deca60196c36280cbb942c1031e652_31bf3856ad364e35_6.1.7600.20737_none_cd8305fc204f6e00.manifest

File version

Not Applicable

File size

697

Date (UTC)

18-Jun-2010

Time (UTC)

14:19

Platform

Not Applicable

File name

Amd64_b3a28370776bbf4aad6d698150c11dd2_31bf3856ad364e35_6.1.7600.20737_none_836155eece42accc.manifest

File version

Not Applicable

File size

1,036

Date (UTC)

18-Jun-2010

Time (UTC)

14:19

Platform

Not Applicable

File name

Amd64_microsoft-windows-wow64_31bf3856ad364e35_6.1.7600.20737_none_c4dc6c5e09f376a8.manifest

File version

Not Applicable

File size

11,008

Date (UTC)

18-Jun-2010

Time (UTC)

14:21

Platform

Not Applicable

File name

Wow64_microsoft-windows-wow64_31bf3856ad364e35_6.1.7600.20737_none_cf3116b03e5438a3.manifest

File version

Not Applicable

File size

12,084

Date (UTC)

18-Jun-2010

Time (UTC)

09:33

Platform

Not Applicable

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

File name

Ia64_42e64950aa8c344092efd47996c9100b_31bf3856ad364e35_6.1.7600.20737_none_02dd2e5d65b822c9.manifest

File version

Not Applicable

File size

696

Date (UTC)

18-Jun-2010

Time (UTC)

14:19

Platform

Not Applicable

File name

Ia64_69282df8059fd83b40ea8cb870b6f290_31bf3856ad364e35_6.1.7600.20737_none_bd68a5b7233610e3.manifest

File version

Not Applicable

File size

695

Date (UTC)

18-Jun-2010

Time (UTC)

14:19

Platform

Not Applicable

File name

Ia64_microsoft-windows-wow64_31bf3856ad364e35_6.1.7600.20737_none_68bf74d051940e6e.manifest

File version

Not Applicable

File size

12,845

Date (UTC)

18-Jun-2010

Time (UTC)

14:19

Platform

Not Applicable

File name

Wow64_microsoft-windows-wow64_31bf3856ad364e35_6.1.7600.20737_none_cf3116b03e5438a3.manifest

File version

Not Applicable

File size

12,084

Date (UTC)

18-Jun-2010

Time (UTC)

09:33

Platform

Not Applicable

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