OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=46525
The issue already existed before oss-fuzz could reproduce it. oss-fuzz found it after qdrawhelper routines were made multithreaded. There might be ways to trigger the issue before that.
Crash type: Stack-use-after-return WRITE 8
Crash state:
QSemaphore::release
std::__1::__function::__func<void handleSpans<BlendSrcGeneric>
FunctionRunnable::run