From 1769846227afafabdcb026bfea42707ea72ae6fb Mon Sep 17 00:00:00 2001
From: Russell Bryant <russell@russellbryant.com>
Date: Fri, 28 Mar 2008 22:52:02 +0000
Subject: [PATCH] Merged revisions 111908-111909 via svnmerge from
 https://origsvn.digium.com/svn/asterisk/trunk

........
r111908 | russell | 2008-03-28 17:45:43 -0500 (Fri, 28 Mar 2008) | 3 lines

Note a minor race condition that I noticed while reviewing Jeff's changes
to this code.

........
r111909 | russell | 2008-03-28 17:50:46 -0500 (Fri, 28 Mar 2008) | 3 lines

Make some notes about common usage of pbx_builtin_getvar_helper() that is not
thread-safe.

........


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.6.0@111910 65c4cc65-6c06-0410-ace0-fbb531ad65f3
---
 doc/janitor-projects.txt | 12 ++++++++++++
 include/asterisk/pbx.h   | 14 ++++++++++++++
 main/dnsmgr.c            |  5 +++++
 3 files changed, 31 insertions(+)

diff --git a/doc/janitor-projects.txt b/doc/janitor-projects.txt
index 9d89ef18ca..b111204f05 100644
--- a/doc/janitor-projects.txt
+++ b/doc/janitor-projects.txt
@@ -1,3 +1,15 @@
+ -- There a bunch of places where the result of pbx_builtin_getvar_helper()
+    gets stored and used.  This is not threadsafe.  This code should be replaced
+	with the following thread-safe version:
+
+	const char *var;
+
+	ast_channel_lock(chan);
+	if ((var = pbx_builtin_getvar_helper(chan, "MYVAR"))) {
+		var = ast_strdupa(var);
+	}
+	ast_channel_unlock(chan);
+
  -- Convert all existing uses of astobj.h to astobj2.h
     -- (chan_sip already in progress in a branch)
 
diff --git a/include/asterisk/pbx.h b/include/asterisk/pbx.h
index 1ba9b0d709..1543de78da 100644
--- a/include/asterisk/pbx.h
+++ b/include/asterisk/pbx.h
@@ -806,6 +806,20 @@ int pbx_builtin_serialize_variables(struct ast_channel *chan, struct ast_str **b
 
 /*!
  * \note Will lock the channel.
+ *
+ * \note This function will return a pointer to the buffer inside the channel
+ * variable.  This value should only be accessed with the channel locked.  If
+ * the value needs to be kept around, it should be done by using the following
+ * thread-safe code:
+ * \code
+ *		const char *var;
+ *
+ *		ast_channel_lock(chan);
+ *		if ((var = pbx_builtin_getvar_helper(chan, "MYVAR"))) {
+ *			var = ast_strdupa(var);
+ *		}
+ *		ast_channel_unlock(chan);
+ * \endcode
  */
 const char *pbx_builtin_getvar_helper(struct ast_channel *chan, const char *name);
 
diff --git a/main/dnsmgr.c b/main/dnsmgr.c
index 0989f63156..19fd1baa7f 100644
--- a/main/dnsmgr.c
+++ b/main/dnsmgr.c
@@ -21,6 +21,11 @@
  * \brief Background DNS update manager
  *
  * \author Kevin P. Fleming <kpfleming@digium.com> 
+ *
+ * \bug There is a minor race condition.  In the event that an IP address
+ * of a dnsmgr managed host changes, there is the potential for the consumer
+ * of that address to access the in_addr data at the same time that the dnsmgr
+ * thread is in the middle of updating it to the new address.
  */
 
 #include "asterisk.h"