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[X86/Funclets] Fix uninitalized values in SoftwareExceptionFrame::UpdateContextFromTransitionBlock #115065

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merged 1 commit into from
Apr 26, 2025
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[X86/Funclets] Fix uninitalized values in SoftwareExceptionFrame::UpdateContextFromTransitionBlock #115065

merged 1 commit into from
Apr 26, 2025
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filipnavara
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This could lead to -1 offset inadvertently not applied in SfiInit for control PC. As a consequence a throw at the very last instruction of try block may not be matched correctly.

@filipnavara
[X86/Funclets] Fix uninitalized values in SoftwareExceptionFrame::Upd…
ceb0947 
…ateContextFromTransitionBlock

This could lead to -1 offset inadvertently not applied in `SfiInit` for control PC. As a consequence a `throw` at the very last instruction of `try` block may not be matched correctly.
@dotnet-policy-service dotnet-policy-service bot added the community-contribution Indicates that the PR has been added by a community member label Apr 25, 2025
@filipnavara filipnavara mentioned this pull request Apr 25, 2025
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@filipnavara filipnavara requested review from jkotas and VSadov April 25, 2025 21:53
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jkotas commented Apr 25, 2025

This could lead to -1 offset inadvertently not applied in SfiInit for control PC.

Do you mean this one?

runtime/src/coreclr/vm/exceptionhandling.cpp

Line 3859 in 32463ba

controlPC -= STACKWALK_CONTROLPC_ADJUST_OFFSET;

Where were the uninitialized values read on this path before this fix?

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filipnavara commented Apr 25, 2025 •
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Do you mean this one?

Yes

Where were the uninitialized values read on this path before this fix?

HasFaulted in the if depends on ContextFlags which were uninitalized. I initialized them to a correct value so we don't accidentally end up with CONTEXT_EXCEPTION_ACTIVE flag there (from random garbage in the allocation that is not zero initialized). The other initializations are not strictly necessary but I think it's better to have them consistent.

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jkotas approved these changes Apr 25, 2025
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Thanks

@jkotas jkotas mentioned this pull request Apr 26, 2025
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@jkotas jkotas merged commit a2779f6 into dotnet:main Apr 26, 2025
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VSadov commented Apr 26, 2025

@filipnavara the change makes sense.
Is this what you think was causing the trouble in async case, or just found along the way?

I could try cherrypicking just this change into async branch.
Not sure about a whole merge from main though as that often breaks other random scenarios.

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am11 commented Apr 26, 2025

Is this what you think was causing the trouble in async case, or just found along the way?

@filipnavara posted here that this was causing the async test failure: dotnet/runtimelab#3100 (comment), so cherry-picking would do the trick.

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VSadov commented Apr 26, 2025

Somehow i am notified of upstream changes/comments more urgently than about comments in labs.
This all makes me happier, either way!!

@filipnavara filipnavara deleted the patch-21 branch April 27, 2025 16:25
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@jkotas jkotas jkotas approved these changes

@VSadov VSadov Awaiting requested review from VSadov

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