From 3eef3f39a646f279e88cdb2fc45b6b17211fcd74 Mon Sep 17 00:00:00 2001
From: Nick Wellnhofer <wellnhofer@aevum.de>
Date: Tue, 20 Jun 2017 16:13:57 +0200
Subject: [PATCH] Fix NULL deref in xmlParseExternalEntityPrivate

If called from xmlParseExternalEntity, oldctxt is NULL which leads to
a NULL deref if an error occurs. This only affects external code that
calls xmlParseExternalEntity.

Patch from David Kilzer with minor changes.

Fixes bug 780159.
---
 parser.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/parser.c b/parser.c
index f561e2fc..cfc5b8e0 100644
--- a/parser.c
+++ b/parser.c
@@ -13224,7 +13224,7 @@ xmlParseExternalEntityPrivate(xmlDocPtr doc, xmlParserCtxtPtr oldctxt,
     /*
      * And record the last error if any
      */
-    if (ctxt->lastError.code != XML_ERR_OK)
+    if ((oldctxt != NULL) && (ctxt->lastError.code != XML_ERR_OK))
         xmlCopyError(&ctxt->lastError, &oldctxt->lastError);
 
     if (sax != NULL)