Issue #23782: Fixed possible memory leak in _PyTraceback_Add() and exception

loss in PyTraceBack_Here().

2 files changed, 29 insertions, 20 deletions

diff --git a/Misc/NEWS b/Misc/NEWS
index 2b0397bf7d..5d972fdea8 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,9 @@ What's New in Python 3.6.0 beta 3
 Core and Builtins
 -----------------
 
+- Issue #23782: Fixed possible memory leak in _PyTraceback_Add() and exception
+  loss in PyTraceBack_Here().
+
 Library
 -------
 
diff --git a/Python/traceback.c b/Python/traceback.c
index e8aac1bad8..9f8c568b08 100644
--- a/Python/traceback.c
+++ b/Python/traceback.c
@@ -132,47 +132,53 @@ newtracebackobject(PyTracebackObject *next, PyFrameObject *frame)
 int
 PyTraceBack_Here(PyFrameObject *frame)
 {
-    PyThreadState *tstate = PyThreadState_GET();
-    PyTracebackObject *oldtb = (PyTracebackObject *) tstate->curexc_traceback;
-    PyTracebackObject *tb = newtracebackobject(oldtb, frame);
-    if (tb == NULL)
+    PyObject *exc, *val, *tb, *newtb;
+    PyErr_Fetch(&exc, &val, &tb);
+    newtb = (PyObject *)newtracebackobject((PyTracebackObject *)tb, frame);
+    if (newtb == NULL) {
+        _PyErr_ChainExceptions(exc, val, tb);
         return -1;
-    tstate->curexc_traceback = (PyObject *)tb;
-    Py_XDECREF(oldtb);
+    }
+    PyErr_Restore(exc, val, newtb);
+    Py_XDECREF(tb);
     return 0;
 }
 
 /* Insert a frame into the traceback for (funcname, filename, lineno). */
 void _PyTraceback_Add(const char *funcname, const char *filename, int lineno)
 {
-    PyObject *globals = NULL;
-    PyCodeObject *code = NULL;
-    PyFrameObject *frame = NULL;
-    PyObject *exception, *value, *tb;
+    PyObject *globals;
+    PyCodeObject *code;
+    PyFrameObject *frame;
+    PyObject *exc, *val, *tb;
 
     /* Save and clear the current exception. Python functions must not be
        called with an exception set. Calling Python functions happens when
        the codec of the filesystem encoding is implemented in pure Python. */
-    PyErr_Fetch(&exception, &value, &tb);
+    PyErr_Fetch(&exc, &val, &tb);
 
     globals = PyDict_New();
     if (!globals)
-        goto done;
+        goto error;
     code = PyCode_NewEmpty(filename, funcname, lineno);
-    if (!code)
-        goto done;
+    if (!code) {
+        Py_DECREF(globals);
+        goto error;
+    }
     frame = PyFrame_New(PyThreadState_Get(), code, globals, NULL);
+    Py_DECREF(globals);
+    Py_DECREF(code);
     if (!frame)
-        goto done;
+        goto error;
     frame->f_lineno = lineno;
 
-    PyErr_Restore(exception, value, tb);
+    PyErr_Restore(exc, val, tb);
     PyTraceBack_Here(frame);
+    Py_DECREF(frame);
+    return;
 
-done:
-    Py_XDECREF(globals);
-    Py_XDECREF(code);
-    Py_XDECREF(frame);
+error:
+    _PyErr_ChainExceptions(exc, val, tb);
 }
 
 static PyObject *