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[3.13] gh-120298: Fix use-after-free in list_richcompare_impl (GH-120303) #120340

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Merged
sobolevn merged 1 commit into from
Jun 11, 2024
Merged

[3.13] gh-120298: Fix use-after-free in list_richcompare_impl (GH-120303) #120340

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gh-120298: Fix use-after-free in list_richcompare_impl (GH-120303) 
(cherry picked from commit 141baba)

Co-authored-by: Nikita Sobolev <[email protected]>
Co-authored-by: Serhiy Storchaka <[email protected]>
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@sobolevn @serhiy-storchaka @miss-islington
2 people authored and miss-islington committed Jun 11, 2024
commit 5a2001c474f36d7b9ea163afbe9a682d085bbcc1
11 changes: 11 additions & 0 deletions Lib/test/test_list.py
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Original file line number Diff line number Diff line change
Expand Up @@ -234,6 +234,17 @@ def __eq__(self, other):
list4 = [1]
self.assertFalse(list3 == list4)

def test_lt_operator_modifying_operand(self):
# See gh-120298
class evil:
def __lt__(self, other):
other.clear()
return NotImplemented

a = [[evil()]]
with self.assertRaises(TypeError):
a[0] < a

@cpython_only
def test_preallocation(self):
iterable = [0] * 10
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2024-06-10-10-42-48.gh-issue-120298.napREA.rst
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@@ -0,0 +1,2 @@
Fix use-after free in ``list_richcompare_impl`` which can be invoked via
some specificly tailored evil input.
9 changes: 8 additions & 1 deletion Objects/listobject.c
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Expand Up @@ -3382,7 +3382,14 @@ list_richcompare_impl(PyObject *v, PyObject *w, int op)
}

/* Compare the final item again using the proper operator */
return PyObject_RichCompare(vl->ob_item[i], wl->ob_item[i], op);
PyObject *vitem = vl->ob_item[i];
PyObject *witem = wl->ob_item[i];
Py_INCREF(vitem);
Py_INCREF(witem);
PyObject *result = PyObject_RichCompare(vl->ob_item[i], wl->ob_item[i], op);
Py_DECREF(vitem);
Py_DECREF(witem);
return result;
}

static PyObject *
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