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gh-151763: Fix crash in PyList_New() on allocation failure under low memory #154019

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gh-151763: Fix crash in PyList_New() on allocation failure under low memory #154019

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6ff08d9
Fixed OOM-0004 from gh-151763
Abhi210 Jul 18, 2026
15ee20d
Resolve the comments on the PR 154019
Abhi210 Jul 19, 2026
46a6c11
Resolve more comments on the PR 154019
Abhi210 Jul 19, 2026
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2026-07-18-22-56-27.gh-issue-152125.sEPvJf.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Fix a crash in the :term:`free-threaded build` where :c:func:`PyList_New` could leave
a newly allocated list's item buffer pointer uninitialized when the backing
array allocation failed under low memory, leading to an invalid free.
11 changes: 5 additions & 6 deletions Objects/listobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -252,10 +252,11 @@ PyList_New(Py_ssize_t size)
return NULL;
}
}
if (size <= 0) {
op->ob_item = NULL;
}
else {
op->ob_item = NULL;
Py_SET_SIZE(op, size);
op->allocated = size;

if (size > 0) {
#ifdef Py_GIL_DISABLED
_PyListArray *array = list_allocate_array(size);
if (array == NULL) {
Expand All @@ -272,8 +273,6 @@ PyList_New(Py_ssize_t size)
return PyErr_NoMemory();
}
}
Py_SET_SIZE(op, size);
op->allocated = size;
_PyObject_GC_TRACK(op);
return (PyObject *) op;
}
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