commit aa6c297316a62baed42f10508cf21d781b0fbee4
author Andrew Kuchling <amk@amk.ca> Sat Jun 22 12:33:05 2013 -0400
committer Andrew Kuchling <amk@amk.ca> Sat Jun 22 12:33:05 2013 -0400
tree 992a09204b27e988360e928a838056823d15684d
parent 22b4b4cef4a4ed290d4c4941674f4e472f6bc3dc

#18113: avoid segfault if Py_XDECREF triggers code that calls set_panel_userptr again

Problem noted & original patch by Serhiy Storchaka; I tweaked the patch a bit.

Lib/test/test_curses.py

diff --git a/Lib/test/test_curses.py b/Lib/test/test_curses.py
index 387a185..fcf9618 100644
--- a/Lib/test/test_curses.py
+++ b/Lib/test/test_curses.py
@@ -262,6 +262,14 @@
     if sys.getrefcount(obj) != nrefs:
         raise RuntimeError, "set_userptr leaked references"
 
+def test_userptr_segfault(stdscr):
+    panel = curses.panel.new_panel(stdscr)
+    class A:
+        def __del__(self):
+            panel.set_userptr(None)
+    panel.set_userptr(A())
+    panel.set_userptr(None)
+
 def test_resize_term(stdscr):
     if hasattr(curses, 'resizeterm'):
         lines, cols = curses.LINES, curses.COLS
@@ -281,6 +289,7 @@
         window_funcs(stdscr)
         test_userptr_without_set(stdscr)
         test_userptr_memory_leak(stdscr)
+        test_userptr_segfault(stdscr)
         test_resize_term(stdscr)
         test_issue6243(stdscr)
     finally:

Modules/_curses_panel.c

diff --git a/Modules/_curses_panel.c b/Modules/_curses_panel.c
index dd231e7..bdd5cf0 100644
--- a/Modules/_curses_panel.c
+++ b/Modules/_curses_panel.c
@@ -294,12 +294,17 @@
 PyCursesPanel_set_panel_userptr(PyCursesPanelObject *self, PyObject *obj)
 {
     PyObject *oldobj;
+    int rc;
     PyCursesInitialised;
-    oldobj = (PyObject *) panel_userptr(self->pan);
-    Py_XDECREF(oldobj);
     Py_INCREF(obj);
-    return PyCursesCheckERR(set_panel_userptr(self->pan, (void*)obj),
-                            "set_panel_userptr");
+    oldobj = (PyObject *) panel_userptr(self->pan);
+    rc = set_panel_userptr(self->pan, (void*)obj);
+    if (rc == ERR) {
+        /* In case of an ncurses error, decref the new object again */
+        Py_DECREF(obj);
+    }
+    Py_XDECREF(oldobj);
+    return PyCursesCheckERR(rc, "set_panel_userptr");
 }
 
 static PyObject *