[release/6.0] [iOS][Android] Fix crash in Exception.CaptureDispatchState #71171
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added 3 commits
June 22, 2022 22:31
There is a crash in `Exception.CaptureDispatchState` when called from one thread at the same time another calls into `Exception.RestoreDispatchState`. The reason for the crash is due to the way we do not update `foreignExceptionFrames` in a thread-safe way. `foreignExceptionFrames` is used in both methods and can crash when the size changes before the array is copied. The fix is to lock when reading from and writing to `foreignExceptionFrames`. Fixes #70081
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leecow
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Backport of #70970 to release/6.0
/cc @steveisok
Customer Impact
There exists a race condition in mono's implementation of
Exception.CaptureDispatchStatethat can cause a crash when an exception is re-thrown from anawaitfrom multiple observers. The crash happens whenException.RestoreDispatchStateis called at the same timeException.CaptureDispatchStateis and anArray.Copyfails due to an internal member length change.This is impacting a customer that is trying to move over to MAUI, but can't due to this issue.
Testing
Manual testing of a customer provided reproduction
Risk
Low - the change captures the shared state in a local variable so that
Exception.CaptureDispatchStatecan do its jobIMPORTANT: If this change touches code that ships in a NuGet package, please make certain that you have added any necessary package authoring and gotten it explicitly reviewed.