libxml2: patch security issues

Fixes
CVE-2019-19956
CVE-2020-24977
CVE-2019-20388
CVE-2020-7595

Signed-off-by: Jan Pavlinec <jan.pavlinec@nic.cz>

libs/libxml2/patches/CVE-2019-19956.patch

@@ -0,0 +1,33 @@
+From 5a02583c7e683896d84878bd90641d8d9b0d0549 Mon Sep 17 00:00:00 2001
+From: Zhipeng Xie <xiezhipeng1@huawei.com>
+Date: Wed, 7 Aug 2019 17:39:17 +0800
+Subject: [PATCH] Fix memory leak in xmlParseBalancedChunkMemoryRecover
+
+When doc is NULL, namespace created in xmlTreeEnsureXMLDecl
+is bind to newDoc->oldNs, in this case, set newDoc->oldNs to
+NULL and free newDoc will cause a memory leak.
+
+Found with libFuzzer.
+
+Closes #82.
+---
+ parser.c | 3 ++-
+ 1 file changed, 2 insertions(+), 1 deletion(-)
+
+diff --git a/parser.c b/parser.c
+index 1ce1ccf14..26d9f4e3b 100644
+--- a/parser.c
++++ b/parser.c
+@@ -13894,7 +13894,8 @@ xmlParseBalancedChunkMemoryRecover(xmlDocPtr doc, xmlSAXHandlerPtr sax,
+     xmlFreeParserCtxt(ctxt);
+     newDoc->intSubset = NULL;
+     newDoc->extSubset = NULL;
+-    newDoc->oldNs = NULL;
++    if(doc != NULL)
++	newDoc->oldNs = NULL;
+     xmlFreeDoc(newDoc);
+ 
+     return(ret);
+-- 
+GitLab
+