commit c46f0423a42c46cf62d12c300ec36a848f8ba72c
author Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com> Tue Oct 23 12:45:44 2018 -0700
committer GitHub <noreply@github.com> Tue Oct 23 12:45:44 2018 -0700
tree e2639e9f358a8cc07203f1733ab324df076e52cb
parent 7a253dcd97fa669b8615476b287ef4dd0a935014

Fix error handling bugs in _elementtree.c. (GH-10060)


References could leak, NULL could be dereferenced, and the Expat parser could
be double freed when some errors raised.
(cherry picked from commit 9f3ed3e213b30059087d059a7d1d3b2527fa8654)

Co-authored-by: Zackery Spytz <zspytz@gmail.com>

Modules/_elementtree.c

diff --git a/Modules/_elementtree.c b/Modules/_elementtree.c
index d13c6dd..3118b55 100644
--- a/Modules/_elementtree.c
+++ b/Modules/_elementtree.c
@@ -336,6 +336,9 @@
 get_attrib_from_keywords(PyObject *kwds)
 {
     PyObject *attrib_str = PyUnicode_FromString("attrib");
+    if (attrib_str == NULL) {
+        return NULL;
+    }
     PyObject *attrib = PyDict_GetItem(kwds, attrib_str);
 
     if (attrib) {
@@ -356,10 +359,10 @@
 
     Py_DECREF(attrib_str);
 
-    /* attrib can be NULL if PyDict_New failed */
-    if (attrib)
-        if (PyDict_Update(attrib, kwds) < 0)
-            return NULL;
+    if (attrib != NULL && PyDict_Update(attrib, kwds) < 0) {
+        Py_DECREF(attrib);
+        return NULL;
+    }
     return attrib;
 }
 
@@ -579,10 +582,9 @@
         attrib = PyDict_Copy(attrib);
         if (!attrib)
             return NULL;
-        if (kwds) {
-            if (PyDict_Update(attrib, kwds) < 0) {
-                return NULL;
-            }
+        if (kwds != NULL && PyDict_Update(attrib, kwds) < 0) {
+            Py_DECREF(attrib);
+            return NULL;
         }
     } else if (kwds) {
         /* have keyword args */
@@ -1857,7 +1859,6 @@
              * scheduled for removal.
             */
             if (!(recycle = PyList_New(slicelen))) {
-                PyErr_NoMemory();
                 return -1;
             }
 
@@ -1897,7 +1898,7 @@
             self->extra->length -= slicelen;
 
             /* Discard the recycle list with all the deleted sub-elements */
-            Py_XDECREF(recycle);
+            Py_DECREF(recycle);
             return 0;
         }
 
@@ -3352,7 +3353,6 @@
         if (!target) {
             Py_CLEAR(self->entity);
             Py_CLEAR(self->names);
-            EXPAT(ParserFree)(self->parser);
             return -1;
         }
     }