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bpo-44856: Possible reference leak in error paths of update_bases() and __build_class__ (GH-27647)

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(cherry picked from commit a40675c659)

Co-authored-by: Pablo Galindo Salgado <Pablogsal@gmail.com>
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Miss Islington (bot) 2021-08-07 07:03:17 -07:00 • committed by GitHub
parent 699ee016af
commit ac8f72cd3f
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2 changed files with 14 additions and 22 deletions
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1
Misc/NEWS.d/next/Core and Builtins/2021-08-07-01-26-12.bpo-44856.9rk3li.rst Normal file
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@ -0,0 +1 @@
Fix reference leaks in the error paths of ``update_bases()`` and ``__build_class__``. Patch by Pablo Galindo.

35
Python/bltinmodule.c
View file

@ -72,6 +72,7 @@ update_bases(PyObject *bases, PyObject *const *args, Py_ssize_t nargs)
/* If this is a first successful replacement, create new_bases list and /* If this is a first successful replacement, create new_bases list and
copy previously encountered bases. */ copy previously encountered bases. */
if (!(new_bases = PyList_New(i))) { if (!(new_bases = PyList_New(i))) {
Py_DECREF(new_base);
goto error; goto error;
} }
for (j = 0; j < i; j++) { for (j = 0; j < i; j++) {
@ -82,6 +83,7 @@ update_bases(PyObject *bases, PyObject *const *args, Py_ssize_t nargs)
} }
j = PyList_GET_SIZE(new_bases); j = PyList_GET_SIZE(new_bases);
if (PyList_SetSlice(new_bases, j, j, new_base) < 0) { if (PyList_SetSlice(new_bases, j, j, new_base) < 0) {
Py_DECREF(new_base);
goto error; goto error;
} }
Py_DECREF(new_base); Py_DECREF(new_base);
@ -103,8 +105,9 @@ static PyObject *
builtin___build_class__(PyObject *self, PyObject *const *args, Py_ssize_t nargs, builtin___build_class__(PyObject *self, PyObject *const *args, Py_ssize_t nargs,
PyObject *kwnames) PyObject *kwnames)
{ {
PyObject *func, *name, *bases, *mkw, *meta, *winner, *prep, *ns, *orig_bases; PyObject *func, *name, *winner, *prep;
PyObject *cls = NULL, *cell = NULL; 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 */ int isclass = 0; /* initialize to prevent gcc warning */
if (nargs < 2) { if (nargs < 2) {
@ -141,26 +144,20 @@ builtin___build_class__(PyObject *self, PyObject *const *args, Py_ssize_t nargs,
else { else {
mkw = _PyStack_AsDict(args + nargs, kwnames); mkw = _PyStack_AsDict(args + nargs, kwnames);
if (mkw == NULL) { if (mkw == NULL) {
Py_DECREF(bases); goto error;
return NULL;
} }
meta = _PyDict_GetItemIdWithError(mkw, &PyId_metaclass); meta = _PyDict_GetItemIdWithError(mkw, &PyId_metaclass);
if (meta != NULL) { if (meta != NULL) {
Py_INCREF(meta); Py_INCREF(meta);
if (_PyDict_DelItemId(mkw, &PyId_metaclass) < 0) { if (_PyDict_DelItemId(mkw, &PyId_metaclass) < 0) {
Py_DECREF(meta); goto error;
Py_DECREF(mkw);
Py_DECREF(bases);
return NULL;
} }
/* metaclass is explicitly given, check if it's indeed a class */ /* metaclass is explicitly given, check if it's indeed a class */
isclass = PyType_Check(meta); isclass = PyType_Check(meta);
} }
else if (PyErr_Occurred()) { else if (PyErr_Occurred()) {
Py_DECREF(mkw); goto error;
Py_DECREF(bases);
return NULL;
} }
} }
if (meta == NULL) { if (meta == NULL) {
@ -183,10 +180,7 @@ builtin___build_class__(PyObject *self, PyObject *const *args, Py_ssize_t nargs,
winner = (PyObject *)_PyType_CalculateMetaclass((PyTypeObject *)meta, winner = (PyObject *)_PyType_CalculateMetaclass((PyTypeObject *)meta,
bases); bases);
if (winner == NULL) { if (winner == NULL) {
Py_DECREF(meta); goto error;
Py_XDECREF(mkw);
Py_DECREF(bases);
return NULL;
} }
if (winner != meta) { if (winner != meta) {
Py_DECREF(meta); Py_DECREF(meta);
@ -208,10 +202,7 @@ builtin___build_class__(PyObject *self, PyObject *const *args, Py_ssize_t nargs,
Py_DECREF(prep); Py_DECREF(prep);
} }
if (ns == NULL) { if (ns == NULL) {
Py_DECREF(meta); goto error;
Py_XDECREF(mkw);
Py_DECREF(bases);
return NULL;
} }
if (!PyMapping_Check(ns)) { if (!PyMapping_Check(ns)) {
PyErr_Format(PyExc_TypeError, PyErr_Format(PyExc_TypeError,
@ -252,13 +243,13 @@ builtin___build_class__(PyObject *self, PyObject *const *args, Py_ssize_t nargs,
} }
error: error:
Py_XDECREF(cell); Py_XDECREF(cell);
Py_DECREF(ns); Py_XDECREF(ns);
Py_DECREF(meta); Py_XDECREF(meta);
Py_XDECREF(mkw); Py_XDECREF(mkw);
Py_DECREF(bases);
if (bases != orig_bases) { if (bases != orig_bases) {
Py_DECREF(orig_bases); Py_DECREF(orig_bases);
} }
Py_DECREF(bases);
return cls; return cls;
} }