1358276 - a11y+e10s broken on Windows 10 creators update

Status: RESOLVED FIXED

(Core :: Disability Access APIs, defect)

Description

[(No longer employed by Mozilla) Aaron Klotz]

This is fallout from bug 1348069 which also landed on 55.

Creator's update got rid of the IAccessible typelib on 32-bit and replaced it with a proxy dll. This means that our manifest overrides are invalid on the Creator's Update. :-(

Now I need to figure out a way to handle this gracefully...

Comment 1

[(No longer employed by Mozilla) Aaron Klotz]

A couple of ideas:

1) manually pushing the correct activation context in our startup code only when needed;
2) getting rid of the manifest override and using the updater to fix corrupted IAccessible entries in the registry if they point to missing or non-system components.

Comment 2

[(No longer employed by Mozilla) Aaron Klotz]

The problem is that there is a typelib entry in the registry for the IAccessible interface that is provided by pre-creators update Windows. This registry entry is sometimes modified by third-party software installers to point to a third-party component. The third-party uninstaller does not revert the registry change, however, so some systems are left with a registry value that now points to a non-existent location, thus breaking anything that relied on that system component to be there.

It is particularly bad for Firefox on e10s because it causes marshaling failures which subsequently triggers a fatal IPDL error.

The idea is that we could detect whether the registry entry is dangling and correct it during PostUpdate.

Matt, what is your opinion on this?

Comment 3

[Molly Howell (she/her) (no longer active)]

To make sure I have this right, the plan is to look under the IAccessible typelib entry and make sure the file it points to for 32-bit exists? And if not, point it back to the system oleacc.dll? Yeah, that sounds like something we could do in PostUpdate.

Comment 4

[(No longer employed by Mozilla) Aaron Klotz]

(In reply to Matt Howell [:mhowell] from comment #3)
> To make sure I have this right, the plan is to look under the IAccessible
> typelib entry and make sure the file it points to for 32-bit exists? And if
> not, point it back to the system oleacc.dll? Yeah, that sounds like
> something we could do in PostUpdate.

Pretty much, yeah.

Comment 5

[(No longer employed by Mozilla) Aaron Klotz]

Attachment: Bug 1358276: Add FixCorruptOleAccRegistration to PostUpdate;

Some third-party software tampers with the registry settings for the
IAccessible COM interface which is provided by Windows. If these settings
become corrupted, our a11y implementation breaks. We attempt to detect this
by loading the path to the IAccessible typelib and checking to see if that file
still exists. If it is missing, we reset the typelib GUID and version to the
system default.

The GUIDs and version number included in this patch hold from Windows 7 through
to Windows 10 Anniversary Update. The Windows 10 Creators update does not use
a typelib anymore, so we do nothing in that case. This fix is intended to run
on 32-bit builds only.

Review commit: https://reviewboard.mozilla.org/r/134130/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/134130/

Comment 6

[Molly Howell (she/her) (no longer active)]

Comment on attachment 8862151 [details]
Bug 1358276: Add FixCorruptOleAccRegistration to PostUpdate;

https://reviewboard.mozilla.org/r/134130/#review137026

::: browser/installer/windows/nsis/shared.nsh:933
(Diff revision 1)
> +!define IID_IAccessible "{618736E0-3C3D-11CF-810C-00AA00389B71}"
> +!define CLSID_UniversalMarshaler "{00020404-0000-0000-C000-000000000046}"
> +!define OleAccTypeLib "{1EA4DBF0-3C3B-11CF-810C-00AA00389B71}"
> +!define OleAccTypeLibVersion "1.1"
> +Function FixCorruptOleAccRegistration
> +  ${If} "${ARCH}" == "x64"

Just wrap the whole function in
!ifndef HAVE_64BIT_BUILD
!endif

Comment 7

[(No longer employed by Mozilla) Aaron Klotz]

Comment on attachment 8862151 [details]
Bug 1358276: Add FixCorruptOleAccRegistration to PostUpdate;

Review request updated; see interdiff: https://reviewboard.mozilla.org/r/134130/diff/1-2/

Comment 8

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/22485a2a6eb4
Add FixCorruptOleAccRegistration to PostUpdate; r=mhowell

Comment 9

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/22485a2a6eb4