8000 [3.8] bpo-44856: Possible reference leak in error paths of update_bases() and __build_class__ (GH-27647) by miss-islington · Pull Request #27652 · python/cpython · GitHub
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[3.8] bpo-44856: Possible reference leak in error paths of update_bases() and __build_class__ (GH-27647) #27652

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Merged
merged 1 commit into from
Aug 7, 2021
Merged

[3.8] bpo-44856: Possible reference leak in error paths of update_bases() and __build_class__ (GH-27647) #27652

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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core and Builtins/2021-08-07-01-26-12.bpo-44856.9rk3li.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Fix reference leaks in the error paths of ``update_bases()`` and ``__build_class__``. Patch by Pablo Galindo.
35 changes: 13 additions & 22 deletions Python/bltinmodule.c
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C37B
Original file line number Diff line number Diff line change
Expand Up @@ -71,6 +71,7 @@ update_bases(PyObject *bases, PyObject *const *args, Py_ssize_t nargs)
/* If this is a first successful replacement, create new_bases list and
copy previously encountered bases. */
if (!(new_bases = PyList_New(i))) {
Py_DECREF(new_base);
goto error;
}
for (j = 0; j < i; j++) {
Expand All @@ -81,6 +82,7 @@ update_bases(PyObject *bases, PyObject *const *args, Py_ssize_t nargs)
}
j = PyList_GET_SIZE(new_bases);
if (PyList_SetSlice(new_bases, j, j, new_base) < 0) {
Py_DECREF(new_base);
goto error;
}
Py_DECREF(new_base);
Expand All @@ -102,8 +104,9 @@ static PyObject *
builtin___build_class__(PyObject *self, PyObject *const *args, Py_ssize_t nargs,
PyObject *kwnames)
{
PyObject *func, *name, *bases, *mkw, *meta, *winner, *prep, *ns, *orig_bases;
PyObject *cls = NULL, *cell = NULL;
PyObject *func, *name, *winner, *prep;
PyObject *cls = NULL, *cell = NULL, *ns = NULL, *meta = NULL, *orig_bases = NULL;
PyObject *mkw = NULL, *bases = NULL;
int isclass = 0; /* initialize to prevent gcc warning */

if (nargs < 2) {
Expand Down Expand Up @@ -140,26 +143,20 @@ builtin___build_class__(PyObject *self, PyObject *const *args, Py_ssize_t nargs,
else {
mkw = _PyStack_AsDict(args + nargs, kwnames);
if (mkw == NULL) {
Py_DECREF(bases);
return NULL;
goto error;
}

meta = _PyDict_GetItemIdWithError(mkw, &PyId_metaclass);
if (meta != NULL) {
Py_INCREF(meta);
if (_PyDict_DelItemId(mkw, &PyId_metaclass) < 0) {
Py_DECREF(meta);
Py_DECREF(mkw);
Py_DECREF(bases);
return NULL;
goto error;
}
/* metaclass is explicitly given, check if it's indeed a class */
isclass = PyType_Check(meta);
}
else if (PyErr_Occurred()) {
Py_DECREF(mkw);
Py_DECREF(bases);
return NULL;
goto error;
}
}
if (meta == NULL) {
Expand All @@ -182,10 +179,7 @@ builtin___build_class__(PyObject *self, PyObject *const *args, Py_ssize_t nargs,
winner = (PyObject *)_PyType_CalculateMetaclass((PyTypeObject *)meta,
bases);
if (winner == NULL) {
Py_DECREF(meta);
Py_XDECREF(mkw);
Py_DECREF(bases);
return NULL;
goto error;
}
if (winner != meta) {
Py_DECREF(meta);
Expand All @@ -207,10 +201,7 @@ builtin___build_class__(PyObject *self, PyObject *const *args, Py_ssize_t nargs,
Py_DECREF(prep);
}
if (ns == NULL) {
Py_DECREF(meta);
Py_XDECREF(mkw);
Py_DECREF(bases);
return NULL;
goto error;
}
if (!PyMapping_Check(ns)) {
PyErr_Format(PyExc_TypeError,
Expand Down Expand Up @@ -251,13 +242,13 @@ builtin___build_class__(PyObject *self, PyObject *const *args, Py_ssize_t nargs,
}
error:
Py_XDECREF(cell);
Py_DECREF(ns);
Py_DECREF(meta);
Py_XDECREF(ns);
Py_XDECREF(meta);
Py_XDECREF(mkw);
Py_DECREF(bases);
if (bases != orig_bases) {
Py_DECREF(orig_bases);
}
Py_DECREF(bases);
return cls;
}

Expand Down
0