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[3.8] gh-97616: list_resize() checks for integer overflow (GH-97617) #97628

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Merged
merged 1 commit into from
Oct 4, 2022
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[3.8] gh-97616: list_resize() checks for integer overflow (GH-97617) #97628

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13 changes: 13 additions & 0 deletions Lib/test/test_list.py
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Original file line number Diff line number Diff line change
Expand Up @@ -68,6 +68,19 @@ def imul(a, b): a *= b
self.assertRaises((MemoryError, OverflowError), mul, lst, n)
self.assertRaises((MemoryError, OverflowError), imul, lst, n)

def test_list_resize_overflow(self):
# gh-97616: test new_allocated * sizeof(PyObject*) overflow
# check in list_resize()
lst = [0] * 65
del lst[1:]
self.assertEqual(len(lst), 1)

size = ((2 ** (tuple.__itemsize__ * 8) - 1) // 2)
with self.assertRaises((MemoryError, OverflowError)):
lst * size
with self.assertRaises((MemoryError, OverflowError)):
lst *= size

def test_repr_large(self):
# Check the repr of large list objects
def check(n):
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Security/2022-09-28-17-09-37.gh-issue-97616.K1e3Xs.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Fix multiplying a list by an integer (``list *= int``): detect the integer
overflow when the new allocated length is close to the maximum size. Issue
reported by Jordan Limor. Patch by Victor Stinner.
10 changes: 8 additions & 2 deletions Objects/listobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -66,8 +66,14 @@ list_resize(PyListObject *self, Py_ssize_t newsize)

if (newsize == 0)
new_allocated = 0;
num_allocated_bytes = new_allocated * sizeof(PyObject *);
items = (PyObject **)PyMem_Realloc(self->ob_item, num_allocated_bytes);
if (new_allocated <= (size_t)PY_SSIZE_T_MAX / sizeof(PyObject *)) {
num_allocated_bytes = new_allocated * sizeof(PyObject *);
items = (PyObject **)PyMem_Realloc(self->ob_item, num_allocated_bytes);
}
else {
// integer overflow
items = NULL;
}
if (items == NULL) {
PyErr_NoMemory();
return -1;
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