From 76ecfff7b692620b726bd61878b603420fd9b1e6 Mon Sep 17 00:00:00 2001
From: Norman Feske <norman.feske@genode-labs.com>
Date: Thu, 19 Jun 2014 17:17:33 +0200
Subject: [PATCH] os: Handle corner case in Xml_node::sub_node

When calling 'sub_node' on a node with no sub nodes, the Xml_node would
interpret the characters after the current node while searching for sub
nodes. The patch adds a sanity check that lets the 'sub_node' function
throw an exception when called on a node with no sub nodes.
---
 repos/os/include/util/xml_node.h | 34 +++++++++++++++++++-------------
 1 file changed, 20 insertions(+), 14 deletions(-)

diff --git a/repos/os/include/util/xml_node.h b/repos/os/include/util/xml_node.h
index b62eecb93f..cfc338c09f 100644
--- a/repos/os/include/util/xml_node.h
+++ b/repos/os/include/util/xml_node.h
@@ -621,13 +621,16 @@ namespace Genode {
 			 */
 			Xml_node sub_node(unsigned idx = 0U) const
 			{
-				/* look up node at specified index */
-				try {
-					Xml_node curr_node = _sub_node(content_addr());
-					for (; idx > 0; idx--)
-						curr_node = curr_node.next();
-					return curr_node;
-				} catch (Invalid_syntax) { }
+				if (_num_sub_nodes > 0) {
+
+					/* look up node at specified index */
+					try {
+						Xml_node curr_node = _sub_node(content_addr());
+						for (; idx > 0; idx--)
+							curr_node = curr_node.next();
+						return curr_node;
+					} catch (Invalid_syntax) { }
+				}
 
 				throw Nonexistent_sub_node();
 			}
@@ -639,13 +642,16 @@ namespace Genode {
 			 */
 			Xml_node sub_node(const char *type) const
 			{
-				/* search for sub node of specified type */
-				try {
-					Xml_node curr_node = _sub_node(content_addr());
-					for ( ; true; curr_node = curr_node.next())
-						if (curr_node.has_type(type))
-							return curr_node;
-				} catch (...) { }
+				if (_num_sub_nodes > 0) {
+
+					/* search for sub node of specified type */
+					try {
+						Xml_node curr_node = _sub_node(content_addr());
+						for ( ; true; curr_node = curr_node.next())
+							if (curr_node.has_type(type))
+								return curr_node;
+					} catch (...) { }
+				}
 
 				throw Nonexistent_sub_node();
 			}