bpo-41993: Fix possible issues in remove_module() (GH-22631) (GH-22647)
* PyMapping_HasKey() is not safe because it silences all exceptions and can return incorrect result.
* Informative exceptions from PyMapping_DelItem() are overridden with RuntimeError and
the original exception raised before calling remove_module() is lost.
* There is a race condition between PyMapping_HasKey() and PyMapping_DelItem().
(cherry picked from commit 8287aadb75f6bd0154996424819334cd3839707c)
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
diff --git a/Python/import.c b/Python/import.c
index 0e2e7c3..5e39a2f 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -905,7 +905,11 @@
}
-/* Remove name from sys.modules, if it's there. */
+/* Remove name from sys.modules, if it's there.
+ * Can be called with an exception raised.
+ * If fail to remove name a new exception will be chained with the old
+ * exception, otherwise the old exception is preserved.
+ */
static void
remove_module(PyThreadState *tstate, PyObject *name)
{
@@ -913,18 +917,17 @@
_PyErr_Fetch(tstate, &type, &value, &traceback);
PyObject *modules = tstate->interp->modules;
- if (!PyMapping_HasKey(modules, name)) {
- goto out;
+ if (PyDict_CheckExact(modules)) {
+ PyObject *mod = _PyDict_Pop(modules, name, Py_None);
+ Py_XDECREF(mod);
}
- if (PyMapping_DelItem(modules, name) < 0) {
- _PyErr_SetString(tstate, PyExc_RuntimeError,
- "deleting key in sys.modules failed");
- _PyErr_ChainExceptions(type, value, traceback);
- return;
+ else if (PyMapping_DelItem(modules, name) < 0) {
+ if (_PyErr_ExceptionMatches(tstate, PyExc_KeyError)) {
+ _PyErr_Clear(tstate);
+ }
}
-out:
- _PyErr_Restore(tstate, type, value, traceback);
+ _PyErr_ChainExceptions(type, value, traceback);
}