libxml2: Fix CVE-2020-24977

GNOME project libxml2 v2.9.10 and earlier have a global Buffer Overflow
vulnerability in xmlEncodeEntitiesInternal at libxml2/entities.c. The issue has
been fixed in commit 8e7c20a1 (20910-GITv2.9.10-103-g8e7c20a1).

Reference:
https://gitlab.gnome.org/GNOME/libxml2/-/issues/178

Upstream patch:
50f06b3efb

(From OE-Core rev: d5406b389fcae8fb0f5fc9cc7dbf7ee819c04bc8)

Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 92dc02b8f03f3586de0a2ec1463b189a3918e303)
Signed-off-by: Steve Sakoman <steve@sakoman.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-core/libxml/libxml2/CVE-2020-24977.patch

@@ -0,0 +1,41 @@
+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.
+
+CVE: CVE-2020-24977
+Upstream-Status: Backport [https://gitlab.gnome.org/GNOME/libxml2/-/commit/50f06b3efb638efb0abd95dc62dca05ae67882c2]
+
+Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
+---
+ xmllint.c | 6 ++++++
+ 1 file changed, 6 insertions(+)
+
+diff --git a/xmllint.c b/xmllint.c
+index f6a8e463..c647486f 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);
+-- 
+2.17.1
+

meta/recipes-core/libxml/libxml2_2.9.10.bb

@@ -22,6 +22,7 @@ SRC_URI = "http://www.xmlsoft.org/sources/libxml2-${PV}.tar.gz;name=libtar \
            file://fix-execution-of-ptests.patch \
            file://CVE-2020-7595.patch \
            file://CVE-2019-20388.patch \
+           file://CVE-2020-24977.patch \
            "
 
 SRC_URI[libtar.md5sum] = "10942a1dc23137a8aa07f0639cbfece5"