[Python-checkins] bpo-45329: Fix freed memory access in pyexpat.c (GH-28649)

[serhiy-storchaka]

https://github.com/python/cpython/commit/0742abdc48886b74ed3b66985a54bb1c32802670
commit: 0742abdc48886b74ed3b66985a54bb1c32802670
branch: main
author: TAGAMI Yukihiro <tagami.yukihiro at gmail.com>
committer: serhiy-storchaka <storchaka at gmail.com>
date: 2021-10-02T12:57:13+03:00
summary:

bpo-45329: Fix freed memory access in pyexpat.c (GH-28649)

files:
A Misc/NEWS.d/next/Library/2021-10-01-13-09-53.bpo-45329.9iMYaO.rst
M Modules/pyexpat.c

diff --git a/Misc/NEWS.d/next/Library/2021-10-01-13-09-53.bpo-45329.9iMYaO.rst b/Misc/NEWS.d/next/Library/2021-10-01-13-09-53.bpo-45329.9iMYaO.rst
new file mode 100644
index 0000000000000..b4bedbc278edf
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-10-01-13-09-53.bpo-45329.9iMYaO.rst
@@ -0,0 +1,2 @@
+Fix freed memory access in :class:`pyexpat.xmlparser` when building it with an
+installed expat library <= 2.2.0.
diff --git a/Modules/pyexpat.c b/Modules/pyexpat.c
index ec684638ead11..b3d9bdda7e7ac 100644
--- a/Modules/pyexpat.c
+++ b/Modules/pyexpat.c
@@ -1204,10 +1204,10 @@ static void
 xmlparse_dealloc(xmlparseobject *self)
 {
     PyObject_GC_UnTrack(self);
+    (void)xmlparse_clear(self);
     if (self->itself != NULL)
         XML_ParserFree(self->itself);
     self->itself = NULL;
-    (void)xmlparse_clear(self);
 
     if (self->handlers != NULL) {
         PyMem_Free(self->handlers);