Libguestfs - Nov 2019 - [PATCH] Python: Fix GIL usage in guestfs_int_py_event_callback_wrapper (RHBZ#1773520)

All Py_* functions should be protected by the GIL.
Otherwise internal python data structures can get corrupted.

Move PyGILState_Ensure to the beginning of the block and
PyGILState_Release to the bottom.

Signed-off-by: Sam Eiderman <sameid@google.com>
---
 python/handle.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/python/handle.c b/python/handle.c
index ffd0794d8..659bb5b06 100644
--- a/python/handle.c
+++ b/python/handle.c
@@ -112,13 +112,17 @@ guestfs_int_py_event_callback_wrapper (guestfs_h *g,
                                    const char *buf, size_t buf_len,
                                    const uint64_t *array, size_t array_len)
 {
-  PyGILState_STATE py_save = PyGILState_UNLOCKED;
+  PyGILState_STATE py_save;
   PyObject *py_callback = callback;
   PyObject *py_array;
   PyObject *args;
   PyObject *a;
   size_t i;
   PyObject *py_r;
+  int threads_initialized = PyEval_ThreadsInitialized ();
+
+  if (threads_initialized)
+    py_save = PyGILState_Ensure ();
 
   py_array = PyList_New (array_len);
   for (i = 0; i < array_len; ++i) {
@@ -132,14 +136,8 @@ guestfs_int_py_event_callback_wrapper (guestfs_h *g,
                         buf, buf_len, py_array);
   Py_INCREF (args);
 
-  if (PyEval_ThreadsInitialized ())
-    py_save = PyGILState_Ensure ();
-
   py_r = PyObject_CallObject (py_callback, args);
 
-  if (PyEval_ThreadsInitialized ())
-    PyGILState_Release (py_save);
-
   Py_DECREF (args);
 
   if (py_r != NULL)
@@ -147,6 +145,9 @@ guestfs_int_py_event_callback_wrapper (guestfs_h *g,
   else
     /* Callback threw an exception: print it. */
     PyErr_PrintEx (0);
+
+  if (threads_initialized)
+    PyGILState_Release (py_save);
 }
 
 PyObject *
-- 
2.24.0.432.g9d3f5f5b63-goog