https://github.com/python/cpython/commit/da79ac9d26860db62500762c95b7ae534638f9a7
commit: da79ac9d26860db62500762c95b7ae534638f9a7
branch: main
author: Victor Stinner <vstin...@python.org>
committer: vstinner <vstin...@python.org>
date: 2025-07-03T14:51:44+02:00
summary:
gh-135075: Make PyObject_SetAttr() fail with NULL value and exception (#136180)
Make PyObject_SetAttr() and PyObject_SetAttrString() fail if called
with NULL value and an exception set.
files:
A Misc/NEWS.d/next/C_API/2025-07-01-16-22-39.gh-issue-135075.angu3J.rst
M Doc/c-api/object.rst
M Lib/test/test_capi/test_abstract.py
M Modules/_testcapi/abstract.c
M Objects/object.c
diff --git a/Doc/c-api/object.rst b/Doc/c-api/object.rst
index 0fd159f1eb87f8..21fa1491b33d86 100644
--- a/Doc/c-api/object.rst
+++ b/Doc/c-api/object.rst
@@ -197,6 +197,13 @@ Object Protocol
in favour of using :c:func:`PyObject_DelAttr`, but there are currently no
plans to remove it.
+ The function must not be called with ``NULL`` *v* and an an exception set.
+ This case can arise from forgetting ``NULL`` checks and would delete the
+ attribute.
+
+ .. versionchanged:: next
+ Must not be called with NULL value if an exception is set.
+
.. c:function:: int PyObject_SetAttrString(PyObject *o, const char *attr_name,
PyObject *v)
@@ -207,6 +214,10 @@ Object Protocol
If *v* is ``NULL``, the attribute is deleted, but this feature is
deprecated in favour of using :c:func:`PyObject_DelAttrString`.
+ The function must not be called with ``NULL`` *v* and an an exception set.
+ This case can arise from forgetting ``NULL`` checks and would delete the
+ attribute.
+
The number of different attribute names passed to this function
should be kept small, usually by using a statically allocated string
as *attr_name*.
@@ -215,6 +226,10 @@ Object Protocol
For more details, see :c:func:`PyUnicode_InternFromString`, which may be
used internally to create a key object.
+ .. versionchanged:: next
+ Must not be called with NULL value if an exception is set.
+
+
.. c:function:: int PyObject_GenericSetAttr(PyObject *o, PyObject *name,
PyObject *value)
Generic attribute setter and deleter function that is meant
diff --git a/Lib/test/test_capi/test_abstract.py
b/Lib/test/test_capi/test_abstract.py
index 7d548ae87c0fa6..3a2ed9f5db82f0 100644
--- a/Lib/test/test_capi/test_abstract.py
+++ b/Lib/test/test_capi/test_abstract.py
@@ -1077,6 +1077,31 @@ def test_iter_nextitem(self):
with self.assertRaisesRegex(TypeError, regex):
PyIter_NextItem(10)
+ def test_object_setattr_null_exc(self):
+ class Obj:
+ pass
+ obj = Obj()
+ obj.attr = 123
+
+ exc = ValueError("error")
+ with self.assertRaises(SystemError) as cm:
+ _testcapi.object_setattr_null_exc(obj, 'attr', exc)
+ self.assertIs(cm.exception.__context__, exc)
+ self.assertIsNone(cm.exception.__cause__)
+ self.assertHasAttr(obj, 'attr')
+
+ with self.assertRaises(SystemError) as cm:
+ _testcapi.object_setattrstring_null_exc(obj, 'attr', exc)
+ self.assertIs(cm.exception.__context__, exc)
+ self.assertIsNone(cm.exception.__cause__)
+ self.assertHasAttr(obj, 'attr')
+
+ with self.assertRaises(SystemError) as cm:
+ # undecodable name
+ _testcapi.object_setattrstring_null_exc(obj, b'\xff', exc)
+ self.assertIs(cm.exception.__context__, exc)
+ self.assertIsNone(cm.exception.__cause__)
+
if __name__ == "__main__":
unittest.main()
diff --git
a/Misc/NEWS.d/next/C_API/2025-07-01-16-22-39.gh-issue-135075.angu3J.rst
b/Misc/NEWS.d/next/C_API/2025-07-01-16-22-39.gh-issue-135075.angu3J.rst
new file mode 100644
index 00000000000000..88e0fa65f45dd0
--- /dev/null
+++ b/Misc/NEWS.d/next/C_API/2025-07-01-16-22-39.gh-issue-135075.angu3J.rst
@@ -0,0 +1,2 @@
+Make :c:func:`PyObject_SetAttr` and :c:func:`PyObject_SetAttrString` fail if
+called with ``NULL`` value and an exception set. Patch by Victor Stinner.
diff --git a/Modules/_testcapi/abstract.c b/Modules/_testcapi/abstract.c
index d4045afd515909..c1f769456accef 100644
--- a/Modules/_testcapi/abstract.c
+++ b/Modules/_testcapi/abstract.c
@@ -178,6 +178,42 @@ sequence_fast_get_item(PyObject *self, PyObject *args)
}
+static PyObject *
+object_setattr_null_exc(PyObject *self, PyObject *args)
+{
+ PyObject *obj, *name, *exc;
+ if (!PyArg_ParseTuple(args, "OOO", &obj, &name, &exc)) {
+ return NULL;
+ }
+
+ PyErr_SetObject((PyObject*)Py_TYPE(exc), exc);
+ if (PyObject_SetAttr(obj, name, NULL) < 0) {
+ return NULL;
+ }
+ assert(PyErr_Occurred());
+ return NULL;
+}
+
+
+static PyObject *
+object_setattrstring_null_exc(PyObject *self, PyObject *args)
+{
+ PyObject *obj, *exc;
+ const char *name;
+ Py_ssize_t size;
+ if (!PyArg_ParseTuple(args, "Oz#O", &obj, &name, &size, &exc)) {
+ return NULL;
+ }
+
+ PyErr_SetObject((PyObject*)Py_TYPE(exc), exc);
+ if (PyObject_SetAttrString(obj, name, NULL) < 0) {
+ return NULL;
+ }
+ assert(PyErr_Occurred());
+ return NULL;
+}
+
+
static PyMethodDef test_methods[] = {
{"object_getoptionalattr", object_getoptionalattr, METH_VARARGS},
{"object_getoptionalattrstring", object_getoptionalattrstring,
METH_VARARGS},
@@ -191,6 +227,8 @@ static PyMethodDef test_methods[] = {
{"sequence_fast_get_size", sequence_fast_get_size, METH_O},
{"sequence_fast_get_item", sequence_fast_get_item, METH_VARARGS},
+ {"object_setattr_null_exc", object_setattr_null_exc, METH_VARARGS},
+ {"object_setattrstring_null_exc", object_setattrstring_null_exc,
METH_VARARGS},
{NULL},
};
diff --git a/Objects/object.c b/Objects/object.c
index 1223983753ac46..3ed7d55593dffa 100644
--- a/Objects/object.c
+++ b/Objects/object.c
@@ -1213,16 +1213,27 @@ PyObject_HasAttrString(PyObject *obj, const char *name)
int
PyObject_SetAttrString(PyObject *v, const char *name, PyObject *w)
{
- PyObject *s;
- int res;
+ PyThreadState *tstate = _PyThreadState_GET();
+ if (w == NULL && _PyErr_Occurred(tstate)) {
+ PyObject *exc = _PyErr_GetRaisedException(tstate);
+ _PyErr_SetString(tstate, PyExc_SystemError,
+ "PyObject_SetAttrString() must not be called with NULL value "
+ "and an exception set");
+ _PyErr_ChainExceptions1Tstate(tstate, exc);
+ return -1;
+ }
- if (Py_TYPE(v)->tp_setattr != NULL)
+ if (Py_TYPE(v)->tp_setattr != NULL) {
return (*Py_TYPE(v)->tp_setattr)(v, (char*)name, w);
- s = PyUnicode_InternFromString(name);
- if (s == NULL)
+ }
+
+ PyObject *s = PyUnicode_InternFromString(name);
+ if (s == NULL) {
return -1;
- res = PyObject_SetAttr(v, s, w);
- Py_XDECREF(s);
+ }
+
+ int res = PyObject_SetAttr(v, s, w);
+ Py_DECREF(s);
return res;
}
@@ -1440,6 +1451,16 @@ PyObject_HasAttr(PyObject *obj, PyObject *name)
int
PyObject_SetAttr(PyObject *v, PyObject *name, PyObject *value)
{
+ PyThreadState *tstate = _PyThreadState_GET();
+ if (value == NULL && _PyErr_Occurred(tstate)) {
+ PyObject *exc = _PyErr_GetRaisedException(tstate);
+ _PyErr_SetString(tstate, PyExc_SystemError,
+ "PyObject_SetAttr() must not be called with NULL value "
+ "and an exception set");
+ _PyErr_ChainExceptions1Tstate(tstate, exc);
+ return -1;
+ }
+
PyTypeObject *tp = Py_TYPE(v);
int err;
@@ -1451,8 +1472,7 @@ PyObject_SetAttr(PyObject *v, PyObject *name, PyObject
*value)
}
Py_INCREF(name);
- PyInterpreterState *interp = _PyInterpreterState_GET();
- _PyUnicode_InternMortal(interp, &name);
+ _PyUnicode_InternMortal(tstate->interp, &name);
if (tp->tp_setattro != NULL) {
err = (*tp->tp_setattro)(v, name, value);
Py_DECREF(name);
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