From 9c4b0418218d150f763e46236631c22c32ee134e Mon Sep 17 00:00:00 2001
From: Yaroslav Halchenko <debian@onerussian.com>
Date: Fri, 23 Sep 2011 22:02:50 -0400
Subject: [PATCH] BF: Lock server's executeCmd to prevent racing among iptables
 calls (Closes: #554162)

Many kudos go to Michael Saavedra for the solution and the patch.
---
 server/action.py | 30 +++++++++++++++++++-----------
 1 file changed, 19 insertions(+), 11 deletions(-)

diff --git a/server/action.py b/server/action.py
index 70f4c378..ea79dd86 100644
--- a/server/action.py
+++ b/server/action.py
@@ -25,11 +25,15 @@ __copyright__ = "Copyright (c) 2004 Cyril Jaquier"
 __license__ = "GPL"
 
 import logging, os
+import threading
 #from subprocess import call
 
 # Gets the instance of the logger.
 logSys = logging.getLogger("fail2ban.actions.action")
 
+# Create a lock for running system commands
+_cmd_lock = threading.Lock()
+
 ##
 # Execute commands.
 #
@@ -301,17 +305,21 @@ class Action:
 	#@staticmethod
 	def executeCmd(realCmd):
 		logSys.debug(realCmd)
-		try:
-			# The following line gives deadlock with multiple jails
-			#retcode = call(realCmd, shell=True)
-			retcode = os.system(realCmd)
-			if retcode == 0:
-				logSys.debug("%s returned successfully" % realCmd)
-				return True
-			else:
-				logSys.error("%s returned %x" % (realCmd, retcode))
-		except OSError, e:
-			logSys.error("%s failed with %s" % (realCmd, e))
+		_cmd_lock.acquire()
+		try: # Try wrapped within another try needed for python version < 2.5
+			try:
+				# The following line gives deadlock with multiple jails
+				#retcode = call(realCmd, shell=True)
+				retcode = os.system(realCmd)
+				if retcode == 0:
+					logSys.debug("%s returned successfully" % realCmd)
+					return True
+				else:
+					logSys.error("%s returned %x" % (realCmd, retcode))
+			except OSError, e:
+				logSys.error("%s failed with %s" % (realCmd, e))
+		finally:
+			_cmd_lock.release()
 		return False
 	executeCmd = staticmethod(executeCmd)