fix: null array indexing in CTracer_handle_return by frigus02 · Pull Request #1843 · nedbat/coveragepy (original) (raw)

Fixes #1835

CTracer_set_pdata_stack can initialize self.pdata_stack to an empty stack where ->stack is NULL and ->deph is -1.

Move index into ->stack into ->depth>=0 check to avoid indexing into NULL array.

This issue was found running UndefinedBehaviourSanitizer. It's reproducible in regular test runs, e.g. python3 -m tox -e py311. Adding if (self->pdata_stack->stack == NULL) { fprint(...) } before the moved line shows the issue in several test cases.

The contributing guide mentions ever fix should include tests. I'd be happy to add some, but I'm not quite sure how to do that here. Do you have a preference/advice?