Raise ImportError in subinterpreters for incompatible single-phase init extensions.

Author: ericsnowcurrently

Lib/test/test_import/__init__.py

@@ -1456,6 +1456,22 @@ def check_compatible_shared(self, name, *, strict=False):
         out = os.read(r, 100)
         self.assertEqual(out, b'okay')
 
+    def check_incompatible_shared(self, name):
+        # Differences from check_compatible_shared():
+        #  * verify that import fails
+        #  * "strict" is always True
+        __import__(name)
+
+        r, w = self.pipe()
+        ret = run_in_subinterp_with_config(
+            self.import_script(name, w),
+            **self.RUN_KWARGS,
+            check_multi_interp_extensions=True,
+        )
+        self.assertEqual(ret, 0)
+        out = os.read(r, 100).decode('utf-8')
+        self.assertEqual(out, f'ImportError: module {name} does not support loading in subinterpreters')
+
     def check_compatible_isolated(self, name, *, strict=False):
         # Differences from check_compatible_shared():
         #  * subinterpreter in a new process
@@ -1477,6 +1493,26 @@ def check_compatible_isolated(self, name, *, strict=False):
         self.assertEqual(err, b'')
         self.assertEqual(out, b'okay')
 
+    def check_incompatible_isolated(self, name):
+        # Differences from check_compatible_isolated():
+        #  * verify that import fails
+        #  * "strict" is always True
+        _, out, err = script_helper.assert_python_ok('-c', textwrap.dedent(f'''
+            import _testcapi, sys
+            assert {name!r} not in sys.modules, {name!r}
+            ret = _testcapi.run_in_subinterp_with_config(
+                {self.import_script(name, "sys.stdout.fileno()")!r},
+                **{self.RUN_KWARGS},
+                check_multi_interp_extensions=True,
+            )
+            assert ret == 0, ret
+            '''))
+        self.assertEqual(err, b'')
+        self.assertEqual(
+            out.decode('utf-8'),
+            f'ImportError: module {name} does not support loading in subinterpreters',
+        )
+
     def test_builtin_compat(self):
         module = 'sys'
         with self.subTest(f'{module}: not strict'):
@@ -1500,9 +1536,9 @@ def test_single_init_extension_compat(self):
         with self.subTest(f'{module}: not strict'):
             self.check_compatible_shared(module, strict=False)
         with self.subTest(f'{module}: strict, shared'):
-            self.check_compatible_shared(module)
+            self.check_incompatible_shared(module)
         with self.subTest(f'{module}: strict, isolated'):
-            self.check_compatible_isolated(module)
+            self.check_incompatible_isolated(module)
 
     @unittest.skipIf(_testmultiphase is None, "test requires _testmultiphase module")
     def test_multi_init_extension_compat(self):

Python/import.c

@@ -2442,29 +2442,36 @@ _imp_create_dynamic_impl(PyObject *module, PyObject *spec, PyObject *file)
 
     PyThreadState *tstate = _PyThreadState_GET();
     mod = import_find_extension(tstate, name, path);
-    if (mod != NULL || PyErr_Occurred()) {
-        Py_DECREF(name);
-        Py_DECREF(path);
-        return mod;
+    if (mod != NULL) {
+        const char *name_buf = PyUnicode_AsUTF8(name);
+        assert(name_buf != NULL);
+        if (_PyImport_CheckSubinterpIncompatibleExtensionAllowed(name_buf) < 0) {
+            Py_DECREF(mod);
+            mod = NULL;
+        }
+        goto finally;
+    }
+    else if (PyErr_Occurred()) {
+        goto finally;
     }
 
     if (file != NULL) {
         fp = _Py_fopen_obj(path, "r");
         if (fp == NULL) {
-            Py_DECREF(name);
-            Py_DECREF(path);
-            return NULL;
+            goto finally;
         }
     }
     else
         fp = NULL;
 
     mod = _PyImport_LoadDynamicModuleWithSpec(spec, fp);
 
-    Py_DECREF(name);
-    Py_DECREF(path);
     if (fp)
         fclose(fp);
+
+finally:
+    Py_DECREF(name);
+    Py_DECREF(path);
     return mod;
 }
 

Python/importdl.c

@@ -3,6 +3,7 @@
 
 #include "Python.h"
 #include "pycore_call.h"
+#include "pycore_import.h"
 #include "pycore_pystate.h"
 #include "pycore_runtime.h"
 
@@ -206,6 +207,10 @@ _PyImport_LoadDynamicModuleWithSpec(PyObject *spec, FILE *fp)
 
     /* Fall back to single-phase init mechanism */
 
+    if (_PyImport_CheckSubinterpIncompatibleExtensionAllowed(name_buf) < 0) {
+        goto error;
+    }
+
     if (hook_prefix == nonascii_prefix) {
         /* don't allow legacy init for non-ASCII module names */
         PyErr_Format(