When specializingLOAD_ATTR_SLOT, we don't check whether the given member descriptor is valid for the type we got it from.

Here is a problematic example, where one class "borrows" a slot from another:

>>>classClass:...__slots__= ("slot",)...>>>classSneaky:...borrowed=Class.slot...>>>deff(o):...returno.borrowed...>>>o=Sneaky()

The unspecialized code behaves correctly:

>>>f(o)Traceback (mostrecentcalllast):File"<stdin>",line1,in<module>File"<stdin>",line2,infTypeError:descriptor'slot'for'Class'objectsdoesn't apply to a 'Sneaky'object

However, the specialized code crashes, since it is accessing memory past the end of the object:

>>>f(o)Segmentationfault

We can fix this by performing the same check that the member descriptor performs (PyObject_TypeCheck(obj, descr->d_type)) when specializing.

CC@markshannon

• PR:GH-99257: Check the owner's type when specializing slots #99258

• PR:[3.11] GH-99257: Check the owner's type when specializing slots (GH-99258) #99324