libxml2: Fix CVE-2018-14404

Fix nullptr deref with XPath logic ops

If the XPath stack is corrupted, for example by a misbehaving extension
function, the "and" and "or" XPath operators could dereference NULL
pointers. Check that the XPath stack isn't empty and optimize the
logic operators slightly.

CVE: CVE-2018-14404
(From OE-Core rev: 69315177732a1d260a3315fe8c4c4c44653ae0c8)

Signed-off-by: Andrej Valek <andrej.valek@siemens.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

2 files changed, 46 insertions, 0 deletions

diff --git a/meta/recipes-core/libxml/libxml2/fix-CVE-2018-14404.patch b/meta/recipes-core/libxml/libxml2/fix-CVE-2018-14404.patch
new file mode 100644
index 0000000000..21668e25ad
--- /dev/null
+++ b/meta/recipes-core/libxml/libxml2/fix-CVE-2018-14404.patch
@@ -0,0 +1,45 @@
+libxml2-2.9.8: Fix CVE-2018-14404
+
+[No upstream tracking] -- https://gitlab.gnome.org/GNOME/libxml2/issues/5
+ -- https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=901817
+ -- https://bugzilla.redhat.com/show_bug.cgi?id=1595985
+
+xpath: Fix nullptr deref with XPath logic ops
+
+If the XPath stack is corrupted, for example by a misbehaving extension
+function, the "and" and "or" XPath operators could dereference NULL
+pointers. Check that the XPath stack isn't empty and optimize the
+logic operators slightly.
+
+Upstream-Status: Backport [https://gitlab.gnome.org/GNOME/libxml2/commit/a436374994c47b12d5de1b8b1d191a098fa23594]
+CVE: CVE-2018-14404
+Signed-off-by: Andrej Valek <andrej.valek@siemens.com>
+
+diff --git a/xpath.c b/xpath.c
+index f440696..75cac5c 100644
+--- a/xpath.c
++++ b/xpath.c
+@@ -13297,9 +13297,8 @@ xmlXPathCompOpEval(xmlXPathParserContextPtr ctxt, xmlXPathStepOpPtr op)
+                return(0);
+            }
+             xmlXPathBooleanFunction(ctxt, 1);
+-            arg1 = valuePop(ctxt);
+-            arg1->boolval &= arg2->boolval;
+-            valuePush(ctxt, arg1);
++           if (ctxt->value != NULL)
++               ctxt->value->boolval &= arg2->boolval;
+            xmlXPathReleaseObject(ctxt->context, arg2);
+             return (total);
+         case XPATH_OP_OR:
+@@ -13323,9 +13322,8 @@ xmlXPathCompOpEval(xmlXPathParserContextPtr ctxt, xmlXPathStepOpPtr op)
+                return(0);
+            }
+             xmlXPathBooleanFunction(ctxt, 1);
+-            arg1 = valuePop(ctxt);
+-            arg1->boolval |= arg2->boolval;
+-            valuePush(ctxt, arg1);
++           if (ctxt->value != NULL)
++               ctxt->value->boolval |= arg2->boolval;
+            xmlXPathReleaseObject(ctxt->context, arg2);
+             return (total);
+         case XPATH_OP_EQUAL:
diff --git a/meta/recipes-core/libxml/libxml2_2.9.8.bb b/meta/recipes-core/libxml/libxml2_2.9.8.bb
index 27a648e97a..4ebd2ef383 100644
--- a/meta/recipes-core/libxml/libxml2_2.9.8.bb
+++ b/meta/recipes-core/libxml/libxml2_2.9.8.bb
@@ -21,6 +21,7 @@ SRC_URI = "http://www.xmlsoft.org/sources/libxml2-${PV}.tar.gz;name=libtar \
            file://0001-Make-ptest-run-the-python-tests-if-python-is-enabled.patch \
            file://fix-execution-of-ptests.patch \
            file://fix-CVE-2017-8872.patch \
+           file://fix-CVE-2018-14404.patch \
            "
 
 SRC_URI[libtar.md5sum] = "b786e353e2aa1b872d70d5d1ca0c740d"