diff --git a/‎Lib/test/test_buffer.py‎
Lines changed: 6 additions & 0 deletions b/‎Lib/test/test_buffer.py‎
Lines changed: 6 additions & 0 deletions
diff --git a/‎Misc/NEWS.d/next/C API/2024-01-29-12-13-24.gh-issue-114685.B07RME.rst‎
Lines changed: 3 additions & 0 deletions b/‎Misc/NEWS.d/next/C API/2024-01-29-12-13-24.gh-issue-114685.B07RME.rst‎
Lines changed: 3 additions & 0 deletions
diff --git a/‎Modules/_testcapi/buffer.c‎
Lines changed: 4 additions & 2 deletions b/‎Modules/_testcapi/buffer.c‎
Lines changed: 4 additions & 2 deletions
diff --git a/‎Objects/abstract.c‎
Lines changed: 6 additions & 0 deletions b/‎Objects/abstract.c‎
Lines changed: 6 additions & 0 deletions
@@ -4585,6 +4585,12 @@ def test_c_buffer(self):
             buf.__release_buffer__(mv)
         self.assertEqual(buf.references, 0)
 
+    @unittest.skipIf(_testcapi is None, "requires _testcapi")
+    def test_c_buffer_invalid_flags(self):
+        buf = _testcapi.testBuf()
+        self.assertRaises(SystemError, buf.__buffer__, PyBUF_READ)
+        self.assertRaises(SystemError, buf.__buffer__, PyBUF_WRITE)
+
     def test_inheritance(self):
         class A(bytearray):
             def __buffer__(self, flags):
 
@@ -0,0 +1,3 @@
+:c:func:`PyObject_GetBuffer` now raises a :exc:`SystemError` if called with
+:c:macro:`PyBUF_READ` or :c:macro:`PyBUF_WRITE` as flags. These flags should
+only be used with the ``PyMemoryView_*`` C API.
@@ -54,8 +54,10 @@ static int
 testbuf_getbuf(testBufObject *self, Py_buffer *view, int flags)
 {
     int buf = PyObject_GetBuffer(self->obj, view, flags);
-    Py_SETREF(view->obj, Py_NewRef(self));
-    self->references++;
+    if (buf == 0) {
+        Py_SETREF(view->obj, Py_NewRef(self));
+        self->references++;
+    }
     return buf;
 }
 
 
@@ -425,6 +425,12 @@ PyObject_AsWriteBuffer(PyObject *obj,
 int
 PyObject_GetBuffer(PyObject *obj, Py_buffer *view, int flags)
 {
+    if (flags != PyBUF_SIMPLE) {  /* fast path */
+        if (flags == PyBUF_READ || flags == PyBUF_WRITE) {
+            PyErr_BadInternalCall();
+            return -1;
+        }
+    }
     PyBufferProcs *pb = Py_TYPE(obj)->tp_as_buffer;
 
     if (pb == NULL || pb->bf_getbuffer == NULL) {
Original file line number	Diff line number	Diff line change
@@ -0,0 +1,3 @@
	1	+ :c:func:`PyObject_GetBuffer` now raises a :exc:`SystemError` if called with
	2	+ :c:macro:`PyBUF_READ` or :c:macro:`PyBUF_WRITE` as flags. These flags should
	3	+ only be used with the ``PyMemoryView_*`` C API.
Original file line number	Diff line number	Diff line change
@@ -54,8 +54,10 @@ static int
54	54	testbuf_getbuf(testBufObject self, Py_buffer view, int flags)
55	55	{
56	56	int buf = PyObject_GetBuffer(self->obj, view, flags);
57		- Py_SETREF(view->obj, Py_NewRef(self));
58		- self->references++;
	57	+ if (buf == 0) {
	58	+ Py_SETREF(view->obj, Py_NewRef(self));
	59	+ self->references++;
	60	+ }
59	61	return buf;
60	62	}
61	63