[release/6.0] Fix race condition in InteropSyncBlock for ComWrappers map. #65215
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Approved. We will take for consideration in 6.0.x
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Backport of #65214 to release/6.0
/cc @dotnet/interop-contrib
Customer Impact
There is a race condition for all
ComWrappersscenarios involving creation of a CCW. It is possible that the initial creation of the CCW map on one thread is interpreted as a fully initialized state on another, but this is not the case. A critical section also needed to be initialized but is used prior to that initialization routine being run on the first thread.This issue was observed by a first-party and reported directly to the interop team.
Testing
Since this is a race condition, testing is difficult. Auditing of the code paths for critical section initialization was performed and indicated the issue was possible and confirmed with the state of a DMP file.
Risk
Minimal. The race condition has been removed and the new initialization location is a pay for play location which means performance impact is negligible relative to the creation of the Interop data structure.