diff options
| -rw-r--r-- | Lib/test/test_isinstance.py | 30 | ||||
| -rw-r--r-- | Misc/NEWS.d/next/Core and Builtins/2021-10-19-01-04-08.bpo-30570._G30Ms.rst | 1 | ||||
| -rw-r--r-- | Objects/abstract.c | 20 |
3 files changed, 45 insertions, 6 deletions
diff --git a/Lib/test/test_isinstance.py b/Lib/test/test_isinstance.py index 109c3f8..6ab44be 100644 --- a/Lib/test/test_isinstance.py +++ b/Lib/test/test_isinstance.py @@ -313,6 +313,36 @@ class TestIsInstanceIsSubclass(unittest.TestCase): self.assertRaises(RecursionError, issubclass, int, X()) self.assertRaises(RecursionError, isinstance, 1, X()) + def test_infinite_recursion_via_bases_tuple(self): + """Regression test for bpo-30570.""" + class Failure(object): + def __getattr__(self, attr): + return (self, None) + + with self.assertRaises(RecursionError): + issubclass(Failure(), int) + + def test_infinite_cycle_in_bases(self): + """Regression test for bpo-30570.""" + class X: + @property + def __bases__(self): + return (self, self, self) + self.assertRaises(RecursionError, issubclass, X(), int) + + def test_infinitely_many_bases(self): + """Regression test for bpo-30570.""" + class X: + def __getattr__(self, attr): + self.assertEqual(attr, "__bases__") + class A: + pass + class B: + pass + A.__getattr__ = B.__getattr__ = X.__getattr__ + return (A(), B()) + self.assertRaises(RecursionError, issubclass, X(), int) + def blowstack(fxn, arg, compare_to): # Make sure that calling isinstance with a deeply nested tuple for its diff --git a/Misc/NEWS.d/next/Core and Builtins/2021-10-19-01-04-08.bpo-30570._G30Ms.rst b/Misc/NEWS.d/next/Core and Builtins/2021-10-19-01-04-08.bpo-30570._G30Ms.rst new file mode 100644 index 0000000..d9ab60c --- /dev/null +++ b/Misc/NEWS.d/next/Core and Builtins/2021-10-19-01-04-08.bpo-30570._G30Ms.rst @@ -0,0 +1 @@ +Fixed a crash in ``issubclass()`` from infinite recursion when searching pathological ``__bases__`` tuples.
\ No newline at end of file diff --git a/Objects/abstract.c b/Objects/abstract.c index 6f7b946..6227ad5 100644 --- a/Objects/abstract.c +++ b/Objects/abstract.c @@ -2557,14 +2557,22 @@ abstract_issubclass(PyObject *derived, PyObject *cls) derived = PyTuple_GET_ITEM(bases, 0); continue; } - for (i = 0; i < n; i++) { - r = abstract_issubclass(PyTuple_GET_ITEM(bases, i), cls); - if (r != 0) - break; - } + break; + } + assert(n >= 2); + if (Py_EnterRecursiveCall(" in __issubclass__")) { Py_DECREF(bases); - return r; + return -1; } + for (i = 0; i < n; i++) { + r = abstract_issubclass(PyTuple_GET_ITEM(bases, i), cls); + if (r != 0) { + break; + } + } + Py_LeaveRecursiveCall(); + Py_DECREF(bases); + return r; } static int |