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bpo-42412: Fix possible leaks and check arguments in PyType_FromModuleAndSpec() (GH-23410) 

* There were leaks if Py_tp_bases is used more than once or if some call is
  failed before setting tp_bases.
* There was a crash if the bases argument or the Py_tp_bases slot is not a tuple.
* The documentation was not accurate.
This commit is contained in:
Serhiy Storchaka 2020-11-21 12:02:53 +02:00 committed by GitHub
parent 01a202ab6b
commit 1db76394ea
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 22 additions and 7 deletions
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6
Doc/c-api/type.rst
View File

@ -157,7 +157,8 @@ The following functions and structs are used to create
If *bases* is a tuple, the created heap type contains all types contained
in it as base types.
If *bases* is ``NULL``, the *Py_tp_base* slot is used instead.
If *bases* is ``NULL``, the *Py_tp_bases* slot is used instead.
If that also is ``NULL``, the *Py_tp_base* slot is used instead.
If that also is ``NULL``, the new type derives from :class:`object`.
The *module* argument can be used to record the module in which the new
@ -253,7 +254,8 @@ The following functions and structs are used to create
* :c:member:`~PyBufferProcs.bf_getbuffer`
* :c:member:`~PyBufferProcs.bf_releasebuffer`
Setting :c:data:`Py_tp_bases` may be problematic on some platforms.
Setting :c:data:`Py_tp_bases` or :c:data:`Py_tp_base` may be
problematic on some platforms.
To avoid issues, use the *bases* argument of
:py:func:`PyType_FromSpecWithBases` instead.

23
Objects/typeobject.c
View File

@ -2977,26 +2977,40 @@ PyType_FromModuleAndSpec(PyObject *module, PyType_Spec *spec, PyObject *bases)
base = slot->pfunc;
else if (slot->slot == Py_tp_bases) {
bases = slot->pfunc;
Py_INCREF(bases);
}
}
if (!bases)
if (!bases) {
bases = PyTuple_Pack(1, base);
if (!bases)
if (!bases)
goto fail;
}
else if (!PyTuple_Check(bases)) {
PyErr_SetString(PyExc_SystemError, "Py_tp_bases is not a tuple");
goto fail;
}
else {
Py_INCREF(bases);
}
}
else
else if (!PyTuple_Check(bases)) {
PyErr_SetString(PyExc_SystemError, "bases is not a tuple");
goto fail;
}
else {
Py_INCREF(bases);
}
/* Calculate best base, and check that all bases are type objects */
base = best_base(bases);
if (base == NULL) {
Py_DECREF(bases);
goto fail;
}
if (!_PyType_HasFeature(base, Py_TPFLAGS_BASETYPE)) {
PyErr_Format(PyExc_TypeError,
"type '%.100s' is not an acceptable base type",
base->tp_name);
Py_DECREF(bases);
goto fail;
}
@ -3008,7 +3022,6 @@ PyType_FromModuleAndSpec(PyObject *module, PyType_Spec *spec, PyObject *bases)
type->tp_as_buffer = &res->as_buffer;
/* Set tp_base and tp_bases */
type->tp_bases = bases;
bases = NULL;
Py_INCREF(base);
type->tp_base = base;