[release/10.0] Don't set security descriptor if the mutex is not owned/new #120115
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jozkee
approved these changes
Sep 25, 2025
artl93
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Backport of #120075 to release/10.0
/cc @ericstj @jozkee
Customer Impact
Customer may hit an
UnauthorizedAccessExceptionwhen using Performance Counter or EventLog APIs. This happens when another user has created theGlobal\netfxperf.1.0orGlobal\netfxeventlog.1.0mutexes. This exception is impossible to predict and will be persistent when hit. The result is the opposite of the intent of the original fix. #110399Fix by only setting the ACL when we create the mutex.
Regression
Regression in .NET 10.0 from #110416
Testing
Manual repro and fix.
Risk
Low, we're just applying a condition to only set the ACL on a Mutex when we are the creator of that mutex.