The direction flag is set incorrectly after an APC during an alterable wait of an exception handler when 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

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: Note 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 nameFile versionFile sizeDateTimePlatform
Ntvdm64.dll6.1.7600.1638516,38414-Jul-200901:41x64
Wow64.dll6.1.7600.20737243,20018-Jun-201009:42x64
Wow64cpu.dll6.1.7600.2073713,31218-Jun-201009:42x64
Wow64win.dll6.1.7600.16385361,98414-Jul-200901:41x64
Acwow64.dll6.1.7600.2073744,03218-Jun-201009:06x86
Instnm.exe6.1.7600.207377,68018-Jun-201006:44x86
Ntvdm64.dll6.1.7600.2073714,33618-Jun-201009:08x86
Setup16.exe3.1.0.191825,60018-Jun-201009:06x86
User.exe6.1.7600.207372,04818-Jun-201006:44x86
Wow32.dll6.1.7600.207375,12018-Jun-201009:04x86
For all supported IA-64-based versions of Windows Server 2008 R2
File nameFile versionFile sizeDateTimePlatform
Ia32exec.bin6.8.6808.08,781,82410-Jun-200921:15Not Applicable
Ntvdm64.dll6.1.7600.1638527,64814-Jul-200901:48IA-64
Wow64.dll6.1.7600.20737580,60818-Jun-201008:44IA-64
Wow64cpu.dll6.1.7600.2073736,86418-Jun-201008:44IA-64
Wow64win.dll6.1.7600.16385716,28814-Jul-200901:50IA-64
Wowia32x.dll6.8.6807.088,57618-Jun-201008:44IA-64
Acwow64.dll6.1.7600.2073744,03218-Jun-201009:06x86
Instnm.exe6.1.7600.207377,68018-Jun-201006:44x86
Ntvdm64.dll6.1.7600.2073714,33618-Jun-201009:08x86
Setup16.exe3.1.0.191825,60018-Jun-201009:06x86
User.exe6.1.7600.207372,04818-Jun-201006:44x86
Wow32.dll6.1.7600.207375,12018-Jun-201009:04x86

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:For more information about APCs, visit the following Microsoft website: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

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 nameAmd64_42e64950aa8c344092efd47996c9100b_31bf3856ad364e35_6.1.7600.20737_none_5efa25eb1e178b03.manifest
File versionNot Applicable
File size697
Date (UTC)18-Jun-2010
Time (UTC)14:19
PlatformNot Applicable
File nameAmd64_43deca60196c36280cbb942c1031e652_31bf3856ad364e35_6.1.7600.20737_none_cd8305fc204f6e00.manifest
File versionNot Applicable
File size697
Date (UTC)18-Jun-2010
Time (UTC)14:19
PlatformNot Applicable
File nameAmd64_b3a28370776bbf4aad6d698150c11dd2_31bf3856ad364e35_6.1.7600.20737_none_836155eece42accc.manifest
File versionNot Applicable
File size1,036
Date (UTC)18-Jun-2010
Time (UTC)14:19
PlatformNot Applicable
File nameAmd64_microsoft-windows-wow64_31bf3856ad364e35_6.1.7600.20737_none_c4dc6c5e09f376a8.manifest
File versionNot Applicable
File size11,008
Date (UTC)18-Jun-2010
Time (UTC)14:21
PlatformNot Applicable
File nameWow64_microsoft-windows-wow64_31bf3856ad364e35_6.1.7600.20737_none_cf3116b03e5438a3.manifest
File versionNot Applicable
File size12,084
Date (UTC)18-Jun-2010
Time (UTC)09:33
PlatformNot Applicable
Additional files for all supported IA-64-based versions of Windows Server 2008 R2
File nameIa64_42e64950aa8c344092efd47996c9100b_31bf3856ad364e35_6.1.7600.20737_none_02dd2e5d65b822c9.manifest
File versionNot Applicable
File size696
Date (UTC)18-Jun-2010
Time (UTC)14:19
PlatformNot Applicable
File nameIa64_69282df8059fd83b40ea8cb870b6f290_31bf3856ad364e35_6.1.7600.20737_none_bd68a5b7233610e3.manifest
File versionNot Applicable
File size695
Date (UTC)18-Jun-2010
Time (UTC)14:19
PlatformNot Applicable
File nameIa64_microsoft-windows-wow64_31bf3856ad364e35_6.1.7600.20737_none_68bf74d051940e6e.manifest
File versionNot Applicable
File size12,845
Date (UTC)18-Jun-2010
Time (UTC)14:19
PlatformNot Applicable
File nameWow64_microsoft-windows-wow64_31bf3856ad364e35_6.1.7600.20737_none_cf3116b03e5438a3.manifest
File versionNot Applicable
File size12,084
Date (UTC)18-Jun-2010
Time (UTC)09:33
PlatformNot Applicable
Properties

Article ID: 2253063 - Last Review: Aug 12, 2010 - Revision: 1

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