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

Comece por Objects/memoryobject.c, na implementação vinculada de PyMemoryView_FromBuffer, e leia a documentação da C-API de PyMemoryView_FromBuffer. Revise o pull request #5937 do PyO3 para entender o requisito de tempo de vida do owner e, em seguida, compare as implicações de compatibilidade de manter o owner com as de introduzir uma nova API. O trabalho estará concluído quando a semântica de ownership estiver decidida, documentada e coberta por testes apropriados do CPython.