[3.11] gh-109521: Fix obscure cases handling in PyImport_GetImporter() (GH-109522) (GH-109781)

serhiy-storchaka · web-flow · commit 6a33529cf0bc · 2023-10-07T16:05:13.000+03:00
PyImport_GetImporter() now sets RuntimeError if it fails to get sys.path_hooks or sys.path_importer_cache or they are not list and dict correspondingly. Previously it could return NULL without setting error in obscure cases, crash or raise SystemError if these attributes have wrong type. (cherry picked from commit 62c7015)
diff --git a/Misc/NEWS.d/next/C API/2023-09-17-21-47-31.gh-issue-109521.JDF6i9.rst b/Misc/NEWS.d/next/C API/2023-09-17-21-47-31.gh-issue-109521.JDF6i9.rst
@@ -0,0 +1,5 @@
+:c:func:`PyImport_GetImporter` now sets RuntimeError if it fails to get
+:data:`sys.path_hooks` or :data:`sys.path_importer_cache` or they are not
+list and dict correspondingly. Previously it could return NULL without
+setting error in obscure cases, crash or raise SystemError if these
+attributes have wrong type.
diff --git a/Python/import.c b/Python/import.c
@@ -951,11 +951,22 @@ PyImport_GetImporter(PyObject *path)
 {
     PyThreadState *tstate = _PyThreadState_GET();
     PyObject *path_importer_cache = PySys_GetObject("path_importer_cache");
+    if (path_importer_cache == NULL) {
+        PyErr_SetString(PyExc_RuntimeError, "lost sys.path_importer_cache");
+        return NULL;
+    }
+    Py_INCREF(path_importer_cache);
     PyObject *path_hooks = PySys_GetObject("path_hooks");
-    if (path_importer_cache == NULL || path_hooks == NULL) {
+    if (path_hooks == NULL) {
+        PyErr_SetString(PyExc_RuntimeError, "lost sys.path_hooks");
+        Py_DECREF(path_importer_cache);
         return NULL;
     }
-    return get_path_importer(tstate, path_importer_cache, path_hooks, path);
+    Py_INCREF(path_hooks);
+    PyObject *importer = get_path_importer(tstate, path_importer_cache, path_hooks, path);
+    Py_DECREF(path_hooks);
+    Py_DECREF(path_importer_cache);
+    return importer;
 }
 
 #if defined(__EMSCRIPTEN__) && defined(PY_CALL_TRAMPOLINE)
