bytearray's__setitem__ implementation currently grabs a reference to its internal buffer before calling_getbyvalue to determine the index that needs assignment._getbyvalue can call into arbitrary python code via__index__ dunders, which could alter the internal buffer and leave said reference dangling.

A prior fix for this issue ensures that bounds checking occurs after_getbyvalue is called. However, python code is capable of resizing the bytearray, resulting in limited but still broken behavior.

This patch ensures that the reference to the internal buffer is fetched only after_getbyvalue is called to prevent it from being held while any python code is run.

• Issue:UAF when writing to a bytearray with an element implementing__index__ with side-effects #91153