xref: /third_party/libxml2/backport-Fix-use-after-free-bugs-when-calling-xmlTextReaderCl.patch

From c50196c13d348025a4843305902bb37df64bae36 Mon Sep 17 00:00:00 2001
From: David Kilzer <ddkilzer@apple.com>
Date: Sun, 10 Apr 2022 20:02:47 -0700
Subject: [PATCH 289/300] Fix use-after-free bugs when calling
 xmlTextReaderClose() before xmlFreeTextReader() on post-validating parser

When creating an xmlTextReaderPtr using xmlReaderForMemory(),
there are two optional API functions that can be used:
- xmlTextReaderClose() may be called prior to calling
  xmlFreeTextReader() to free parsing resources and close the
  xmlTextReaderPtr without freeing it.
- xmlTextReaderCurrentDoc() may be called to return an
  xmlDocPtr that's owned by the caller, and must be free using
  xmlFreeDoc() after calling xmlFreeTextReader().

The use-after-free issues occur when calling
xmlTextReaderClose() before xmlFreeTextReader(), with different
issues occurring depending on whether xmlTextReaderCurrentDoc()
is also called.

* xmlreader.c:
(xmlFreeTextReader):
- Move code to xmlTextReaderClose(), remove duplicate code, and
  call xmlTextReaderClose() if it hasn't been called yet.
(xmlTextReaderClose):
- Move call to xmlFreeNode(reader->faketext) from
  xmlFreeTextReader() to fix a use-after-free bug when calling
  xmlTextReaderClose() before xmlFreeTextReader(), but not when
  using xmlTextReaderCurrentDoc().  The bug was introduced in
  2002 by commit beb70bd39.  In 2009 commit f4653dcd8 fixed the
  use-after-free that occurred every time xmlFreeTextReader()
  was called, but not the case where xmlTextReaderClose() was
  called first.
- Move post-parsing validation code from xmlFreeTextReader() to
  fix a second use-after-free when calling xmlTextReaderClose()
  before xmlFreeTextReader().  This regressed in v2.9.10 with
  commit 57a3af56f.

Reference:https://github.com/GNOME/libxml2/commit/c50196c13d348025a4843305902bb37df64bae36
Conflict:NA

---
 xmlreader.c | 40 ++++++++++++++++++----------------------
 1 file changed, 18 insertions(+), 22 deletions(-)

diff --git a/xmlreader.c b/xmlreader.c
index 72e40b0..989b7c1 100644
--- a/xmlreader.c
+++ b/xmlreader.c
@@ -2319,36 +2319,16 @@ xmlFreeTextReader(xmlTextReaderPtr reader) {
 	xmlFree(reader->patternTab);
     }
 #endif
-    if (reader->faketext != NULL) {
-	xmlFreeNode(reader->faketext);
-    }
+    if (reader->mode != XML_TEXTREADER_MODE_CLOSED)
+        xmlTextReaderClose(reader);
     if (reader->ctxt != NULL) {
         if (reader->dict == reader->ctxt->dict)
 	    reader->dict = NULL;
-#ifdef LIBXML_VALID_ENABLED
-	if ((reader->ctxt->vctxt.vstateTab != NULL) &&
-	    (reader->ctxt->vctxt.vstateMax > 0)){
-#ifdef LIBXML_REGEXP_ENABLED
-            while (reader->ctxt->vctxt.vstateNr > 0)
-                xmlValidatePopElement(&reader->ctxt->vctxt, NULL, NULL, NULL);
-#endif /* LIBXML_REGEXP_ENABLED */
-	    xmlFree(reader->ctxt->vctxt.vstateTab);
-	    reader->ctxt->vctxt.vstateTab = NULL;
-	    reader->ctxt->vctxt.vstateMax = 0;
-	}
-#endif /* LIBXML_VALID_ENABLED */
-	if (reader->ctxt->myDoc != NULL) {
-	    if (reader->preserve == 0)
-		xmlTextReaderFreeDoc(reader, reader->ctxt->myDoc);
-	    reader->ctxt->myDoc = NULL;
-	}
 	if (reader->allocs & XML_TEXTREADER_CTXT)
 	    xmlFreeParserCtxt(reader->ctxt);
     }
     if (reader->sax != NULL)
 	xmlFree(reader->sax);
-    if ((reader->input != NULL)  && (reader->allocs & XML_TEXTREADER_INPUT))
-	xmlFreeParserInputBuffer(reader->input);
     if (reader->buffer != NULL)
         xmlBufFree(reader->buffer);
     if (reader->entTab != NULL)
@@ -2379,7 +2359,23 @@ xmlTextReaderClose(xmlTextReaderPtr reader) {
     reader->node = NULL;
     reader->curnode = NULL;
     reader->mode = XML_TEXTREADER_MODE_CLOSED;
+    if (reader->faketext != NULL) {
+        xmlFreeNode(reader->faketext);
+        reader->faketext = NULL;
+    }
     if (reader->ctxt != NULL) {
+#ifdef LIBXML_VALID_ENABLED
+	if ((reader->ctxt->vctxt.vstateTab != NULL) &&
+	    (reader->ctxt->vctxt.vstateMax > 0)){
+#ifdef LIBXML_REGEXP_ENABLED
+            while (reader->ctxt->vctxt.vstateNr > 0)
+                xmlValidatePopElement(&reader->ctxt->vctxt, NULL, NULL, NULL);
+#endif /* LIBXML_REGEXP_ENABLED */
+	    xmlFree(reader->ctxt->vctxt.vstateTab);
+	    reader->ctxt->vctxt.vstateTab = NULL;
+	    reader->ctxt->vctxt.vstateMax = 0;
+	}
+#endif /* LIBXML_VALID_ENABLED */
 	xmlStopParser(reader->ctxt);
 	if (reader->ctxt->myDoc != NULL) {
 	    if (reader->preserve == 0)
-- 
2.27.0