PyMemoryView_FromBuffer discards owner reference from Py_buffer

Bug report

Bug description:

https://github.com/python/cpython/blob/0274d8304e5eec23de100d827eb4da06ab7fd8aa/Objects/memoryobject.c#L769-L788

This means that if you use PyMemoryView_FromBuffer with a buffer that requires an owner to be kept alive, you get a UAF hazard here.

This is not mentioned in the documentation: https://docs.python.org/3/c-api/memoryview.html#c.PyMemoryView_FromBuffer

An extremely cursory didn't find any vulnerable callers within CPython itself, however this was discovered in the process of implementing https://github.com/PyO3/pyo3/pull/5937 where it definitely would have been an issue.

It seems like there's two possible choices here:

• Change this to keep owner around -- potentially breaks existing callers?
• Document this, and introduce a new API with clearer semantics here.

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Beginne mit Objects/memoryobject.c bei der dort verlinkten Implementierung von PyMemoryView_FromBuffer und lies die Dokumentation der PyMemoryView_FromBuffer C-API. Sieh dir den PyO3 Pull Request #5937 an, um die Anforderung an die Lebensdauer des Owners zu verstehen, und vergleiche anschließend die Kompatibilitätsauswirkungen des Beibehaltens des Owners mit der Einführung einer neuen API. Als erledigt gilt die Aufgabe, wenn die Ownership-Semantik entschieden, dokumentiert und durch geeignete CPython-Tests abgedeckt ist.