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From a436374994c47b12d5de1b8b1d191a098fa23594 Mon Sep 17 00:00:00 2001
From: Nick Wellnhofer <wellnhofer@aevum.de>
Date: Mon, 30 Jul 2018 12:54:38 +0200
Subject: [PATCH] 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.
Closes: https://gitlab.gnome.org/GNOME/libxml2/issues/5
Also see
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=901817
https://bugzilla.redhat.com/show_bug.cgi?id=1595985
This is CVE-2018-14404.
Thanks to Guy Inbar for the report.
---
xpath.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/xpath.c b/xpath.c
index 3fae0bf4..5e3bb9ff 100644
--- a/xpath.c
+++ b/xpath.c
@@ -13234,9 +13234,8 @@ 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:
@@ -13252,9 +13251,8 @@ 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:
--
2.18.1
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