Fix crash when a span is finished twice or used from multiple threads - #1609
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On sentry-native platforms, finishing a span or transaction hands ownership to the SDK, which frees it. The wrappers kept the stale pointer and only locked the setters, so a second Finish, or Finish racing a setter, StartChild or GetTrace on another thread, used freed memory. Wrappers now take their lock for every native call and null the pointer on finish; later calls are no-ops. USentrySpan::Finish gets the IsFinished guard USentryTransaction already had.
limbonaut
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Oct 2, 2026
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I think a double-finish guard makes sense regardless. Otherwise, a second finish would release another reference and repeat the finish work, no? |
jpnurmi
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Oct 2, 2026
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Yeah, probably doesn't help much 🤦♂️
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This PR fixes crashes on Windows, Linux and other
sentry-nativeplatforms when a span or transaction is finished twice, or finished on one thread while another thread is still using it.sentry_span_finish/sentry_transaction_finishhand ownership tosentry-native, which frees the object. The plugin wrappers kept the stale pointer and only locked the tag/data setters, so:Finishtwice on aUSentrySpanfreed the native span twice and corrupted the heap. UnlikeUSentryTransaction,USentrySpan::Finishhad noIsFinished()guard.Finishon one thread while another called a setter,StartChildorGetTraceon the same span or transaction could use freed memory.Key changes
FGenericPlatformSentrySpan/FGenericPlatformSentryTransactiontake their lock around every native call and set the native pointer to null after finishing. Later calls are no-ops, andIsFinished()is now based on that pointer, replacing the separate flag.USentrySpan::Finish/FinishWithTimestampnow checkIsFinished(), asUSentryTransactionalready did.