gnu: libxml2: Fix CVE-2017-15412.

* gnu/packages/patches/libxml2-CVE-2017-15412.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/xml.scm (libxml2/fixed)[source]: Use it.

gnu/local.mk

@@ -862,6 +862,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/libxml2-CVE-2017-7376.patch		\
   %D%/packages/patches/libxml2-CVE-2017-9047+CVE-2017-9048.patch	\
   %D%/packages/patches/libxml2-CVE-2017-9049+CVE-2017-9050.patch	\
+  %D%/packages/patches/libxml2-CVE-2017-15412.patch		\
   %D%/packages/patches/libxslt-generated-ids.patch		\
   %D%/packages/patches/libxslt-CVE-2016-4738.patch		\
   %D%/packages/patches/libxslt-CVE-2017-5029.patch		\

gnu/packages/patches/libxml2-CVE-2017-15412.patch

+Fix CVE-2017-15412:
+
+https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-15412
+https://bugs.chromium.org/p/chromium/issues/detail?id=727039
+https://bugzilla.redhat.com/show_bug.cgi?id=1523128
+https://bugzilla.gnome.org/show_bug.cgi?id=783160
+
+Patch copied from upstream source repository:
+
+https://git.gnome.org/browse/libxml2/commit/?id=0f3b843b3534784ef57a4f9b874238aa1fda5a73
+
+From 0f3b843b3534784ef57a4f9b874238aa1fda5a73 Mon Sep 17 00:00:00 2001
+From: Nick Wellnhofer <wellnhofer@aevum.de>
+Date: Thu, 1 Jun 2017 23:12:19 +0200
+Subject: [PATCH] Fix XPath stack frame logic
+
+Move the calls to xmlXPathSetFrame and xmlXPathPopFrame around in
+xmlXPathCompOpEvalPositionalPredicate to make sure that the context
+object on the stack is actually protected. Otherwise, memory corruption
+can occur when calling sloppily coded XPath extension functions.
+
+Fixes bug 783160.
+---
+ xpath.c | 4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/xpath.c b/xpath.c
+index 94815075..b816bd36 100644
+--- a/xpath.c
++++ b/xpath.c
+@@ -11932,11 +11932,11 @@ xmlXPathCompOpEvalPositionalPredicate(xmlXPathParserContextPtr ctxt,
+ 		}
+ 	    }
+ 
+-            frame = xmlXPathSetFrame(ctxt);
+ 	    valuePush(ctxt, contextObj);
++            frame = xmlXPathSetFrame(ctxt);
+ 	    res = xmlXPathCompOpEvalToBoolean(ctxt, exprOp, 1);
+-            tmp = valuePop(ctxt);
+             xmlXPathPopFrame(ctxt, frame);
++            tmp = valuePop(ctxt);
+ 
+ 	    if ((ctxt->error != XPATH_EXPRESSION_OK) || (res == -1)) {
+                 while (tmp != contextObj) {
+-- 
+2.15.1
+

gnu/packages/xml.scm

@@ -155,7 +155,8 @@ (define libxml2/fixed
                         "libxml2-CVE-2017-7375.patch"
                         "libxml2-CVE-2017-7376.patch"
                         "libxml2-CVE-2017-9047+CVE-2017-9048.patch"
-                        "libxml2-CVE-2017-9049+CVE-2017-9050.patch")))))))
+                        "libxml2-CVE-2017-9049+CVE-2017-9050.patch"
+                        "libxml2-CVE-2017-15412.patch")))))))
 
 (define-public python-libxml2
   (package (inherit libxml2)