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-2020-24977.patch

@@ -0,0 +1,36 @@
+From 50f06b3efb638efb0abd95dc62dca05ae67882c2 Mon Sep 17 00:00:00 2001
+From: Nick Wellnhofer <wellnhofer@aevum.de>
+Date: Fri, 7 Aug 2020 21:54:27 +0200
+Subject: [PATCH] Fix out-of-bounds read with 'xmllint --htmlout'
+
+Make sure that truncated UTF-8 sequences don't cause an out-of-bounds
+array access.
+
+Thanks to @SuhwanSong and the Agency for Defense Development (ADD) for
+the report.
+
+Fixes #178.
+---
+ xmllint.c | 6 ++++++
+ 1 file changed, 6 insertions(+)
+
+diff --git a/xmllint.c b/xmllint.c
+index f6a8e4636..c647486f3 100644
+--- a/xmllint.c
++++ b/xmllint.c
+@@ -528,6 +528,12 @@ static void
+ xmlHTMLEncodeSend(void) {
+     char *result;
+ 
++    /*
++     * xmlEncodeEntitiesReentrant assumes valid UTF-8, but the buffer might
++     * end with a truncated UTF-8 sequence. This is a hack to at least avoid
++     * an out-of-bounds read.
++     */
++    memset(&buffer[sizeof(buffer)-4], 0, 4);
+     result = (char *) xmlEncodeEntitiesReentrant(NULL, BAD_CAST buffer);
+     if (result) {
+ 	xmlGenericError(xmlGenericErrorContext, "%s", result);
+-- 
+GitLab
+