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36 lines
1.1 KiB
Python
36 lines
1.1 KiB
Python
"""
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There is a way to put keys of any type in a type's dictionary.
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I think this allows various kinds of crashes, but so far I have only
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found a convoluted attack of _PyType_Lookup(), which uses the mro of the
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type without holding a strong reference to it. Probably works with
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super.__getattribute__() too, which uses the same kind of code.
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"""
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class MyKey(object):
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def __hash__(self):
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return hash('mykey')
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def __eq__(self, other):
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# the following line decrefs the previous X.__mro__
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X.__bases__ = (Base2,)
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# trash all tuples of length 3, to make sure that the items of
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# the previous X.__mro__ are really garbage
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z = []
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for i in range(1000):
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z.append((i, None, None))
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return 0
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class Base(object):
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mykey = 'from Base'
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class Base2(object):
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mykey = 'from Base2'
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# you can't add a non-string key to X.__dict__, but it can be
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# there from the beginning :-)
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X = type('X', (Base,), {MyKey(): 5})
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print(X.mykey)
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# I get a segfault, or a slightly wrong assertion error in a debug build.
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