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gh-148653: Forbid marshalling recursive tuples #155903

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53 changes: 26 additions & 27 deletions Lib/test/test_marshal.py
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Original file line number Diff line number Diff line change
Expand Up @@ -342,14 +342,26 @@ def test_reference_loop_dict(self):
def test_reference_loop_tuple(self):
a = ([],)
a[0].append(a)
for v in range(3):
for v in range(marshal.version + 1):
self.assertRaises(ValueError, marshal.dumps, a, v)

a = ({},)
a[0][None] = a
for v in range(marshal.version + 1):
self.assertRaises(ValueError, marshal.dumps, a, v)

def test_shared_reference_tuple(self):
# A tuple referenced more than once still round-trips with the
# shared identity preserved.
a = (1, 2)
for v in range(3, marshal.version + 1):
d = marshal.dumps(a, v)
b = marshal.loads(d)
self.assertIsInstance(b, tuple)
self.assertIsInstance(b[0], list)
self.assertIs(b[0][0], b)
b = marshal.loads(marshal.dumps([a, a], v))
self.assertEqual(b[0], a)
self.assertIs(b[0], b[1])
big = tuple(range(300)) # too large for TYPE_SMALL_TUPLE
b = marshal.loads(marshal.dumps([big, big]))
self.assertEqual(b[0], big)
self.assertIs(b[0], b[1])

def test_reference_loop_code(self):
def f():
Expand Down Expand Up @@ -399,27 +411,6 @@ def test_loads_reference_loop_dict(self):
self.assertIs(a[None], a)

def test_loads_abnormal_reference_loops(self):
# Indirect self-references of tuples.
data = b'\xa8\x01\x00\x00\x00[\x01\x00\x00\x00r\x00\x00\x00\x00' # ([<R>],)
a = marshal.loads(data)
self.assertIsInstance(a, tuple)
self.assertIsInstance(a[0], list)
self.assertIs(a[0][0], a)

data = b'\xa8\x01\x00\x00\x00{Nr\x00\x00\x00\x000' # ({None: <R>},)
a = marshal.loads(data)
self.assertIsInstance(a, tuple)
self.assertIsInstance(a[0], dict)
self.assertIs(a[0][None], a)

# Direct self-reference which cannot be created in Python.
# This creates a reference loop which cannot be collected.
if False:
data = b'\xa8\x01\x00\x00\x00r\x00\x00\x00\x00' # (<R>,)
a = marshal.loads(data)
self.assertIsInstance(a, tuple)
self.assertIs(a[0], a)

# Direct self-references which cannot be created in Python
# because of unhashability.
data = b'\xfbr\x00\x00\x00\x00N0' # {<R>: None}
Expand All @@ -429,6 +420,8 @@ def test_loads_abnormal_reference_loops(self):

for data in [
# Indirect self-references of immutable objects.
b'\xa8\x01\x00\x00\x00[\x01\x00\x00\x00r\x00\x00\x00\x00', # ([<R>],)
b'\xa8\x01\x00\x00\x00{Nr\x00\x00\x00\x000', # ({None: <R>},)
b'\xba[\x01\x00\x00\x00r\x00\x00\x00\x00NN', # slice([<R>], None)
b'\xbaN[\x01\x00\x00\x00r\x00\x00\x00\x00N', # slice(None, [<R>])
b'\xbaNN[\x01\x00\x00\x00r\x00\x00\x00\x00', # slice(None, None, [<R>])
Expand All @@ -439,12 +432,18 @@ def test_loads_abnormal_reference_loops(self):
b'\xfdN{Nr\x00\x00\x00\x0000', # frozendict({None: {None: <R>})

# Direct self-references which cannot be created in Python.
b'\xa8\x01\x00\x00\x00r\x00\x00\x00\x00', # (<R>,)
b'\xbe\x01\x00\x00\x00r\x00\x00\x00\x00', # frozenset({<R>})
b'\xfdNr\x00\x00\x00\x000', # frozendict({None: <R>})
b'\xfdr\x00\x00\x00\x00N0', # frozendict({<R>: None})
b'\xbar\x00\x00\x00\x00NN', # slice(<R>, None)
b'\xbaNr\x00\x00\x00\x00N', # slice(None, <R>)
b'\xbaNNr\x00\x00\x00\x00', # slice(None, None, <R>)

# Indirect self-references which cannot be created in Python
# because of unhashability.
b'\xa8\x01\x00\x00\x00{r\x00\x00\x00\x00N0', # ({<R>: None},)
b'\xa8\x01\x00\x00\x00<\x01\x00\x00\x00r\x00\x00\x00\x00', # ({<R>},)
]:
with self.subTest(data=data):
self.assertRaises(ValueError, marshal.loads, data)
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2026-08-16-19-33-01.gh-issue-148653.Kt3vQx.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Forbid :mod:`marshalling <marshal>` recursive tuples, and fix a crash when
unmarshalling a self-referencing tuple.
11 changes: 8 additions & 3 deletions Python/marshal.c
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Original file line number Diff line number Diff line change
Expand Up @@ -417,7 +417,9 @@ w_ref(PyObject *v, char *flag, WFILE *p)
}
// Corresponding code should call w_complete() after
// writing the object.
if (PyCode_Check(v) || PySlice_Check(v) || PyFrozenDict_CheckExact(v)) {
if (PyTuple_CheckExact(v) || PyCode_Check(v) || PySlice_Check(v) ||
PyFrozenDict_CheckExact(v))
{
w |= 0x80000000LU;
}
if (_Py_hashtable_set(p->hashtable, Py_NewRef(v),
Expand Down Expand Up @@ -596,6 +598,7 @@ w_complex_object(PyObject *v, char flag, WFILE *p)
for (i = 0; i < n; i++) {
w_object(PyTuple_GET_ITEM(v, i), p);
}
w_complete(v, p);
}
else if (PyList_CheckExact(v)) {
W_TYPE(TYPE_LIST, p);
Expand Down Expand Up @@ -1417,8 +1420,10 @@ r_object(RFILE *p)
break;
}
_read_tuple:
idx = r_ref_reserve(flag, p);
if (idx < 0)
break;
v = PyTuple_New(n);
R_REF(v);
if (v == NULL)
break;

Expand All @@ -1433,7 +1438,7 @@ r_object(RFILE *p)
}
PyTuple_SET_ITEM(v, i, v2);
}
retval = v;
retval = r_ref_insert(v, idx, flag, p);
break;

case TYPE_LIST:
Expand Down
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