gh-109521: Fix obscure cases handling in PyImport_GetImporter() (GH-109522)

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.

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
new file mode 100644 (file)
index 0000000..338650c
--- /dev/null
+++ 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
index 9b0be026f36bc386e68a2954fa5ade09b0c2a19a..5a06cb367e828b84533ba693d453f9517ccc87e9 100644 (file)
--- a/Python/import.c
+++ b/Python/import.c
@@ -2363,9 +2363,14 @@ get_path_importer(PyThreadState *tstate, PyObject *path_importer_cache,
     PyObject *importer;
     Py_ssize_t j, nhooks;
 
-    /* These conditions are the caller's responsibility: */
-    assert(PyList_Check(path_hooks));
-    assert(PyDict_Check(path_importer_cache));
+    if (!PyList_Check(path_hooks)) {
+        PyErr_SetString(PyExc_RuntimeError, "sys.path_hooks is not a list");
+        return NULL;
+    }
+    if (!PyDict_Check(path_importer_cache)) {
+        PyErr_SetString(PyExc_RuntimeError, "sys.path_importer_cache is not a dict");
+        return NULL;
+    }
 
     nhooks = PyList_Size(path_hooks);
     if (nhooks < 0)
@@ -2408,11 +2413,22 @@ 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;
 }