backport libxml2 patch for CVE-2020-7595

related to #1992

Author: flavorjones

patches/libxml2/0005-Fix-infinite-loop-in-xmlStringLenDecodeEntities.patch

@@ -0,0 +1,32 @@
+From 0e1a49c8907645d2e155f0d89d4d9895ac5112b5 Mon Sep 17 00:00:00 2001
+From: Zhipeng Xie <[email protected]>
+Date: Thu, 12 Dec 2019 17:30:55 +0800
+Subject: [PATCH] Fix infinite loop in xmlStringLenDecodeEntities
+
+When ctxt->instate == XML_PARSER_EOF,xmlParseStringEntityRef
+return NULL which cause a infinite loop in xmlStringLenDecodeEntities
+
+Found with libFuzzer.
+
+Signed-off-by: Zhipeng Xie <[email protected]>
+---
+ parser.c | 3 ++-
+ 1 file changed, 2 insertions(+), 1 deletion(-)
+
+diff --git a/parser.c b/parser.c
+index d1c3196..a34bb6c 100644
+--- a/parser.c
++++ b/parser.c
+@@ -2646,7 +2646,8 @@ xmlStringLenDecodeEntities(xmlParserCtxtPtr ctxt, const xmlChar *str, int len,
+     else
+         c = 0;
+     while ((c != 0) && (c != end) && /* non input consuming loop */
+-	   (c != end2) && (c != end3)) {
++           (c != end2) && (c != end3) &&
++           (ctxt->instate != XML_PARSER_EOF)) {
+ 
+ 	if (c == 0) break;
+         if ((c == '&') && (str[1] == '#')) {
+-- 
+2.17.1
+