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.

git-svn-id: https://fail2ban.svn.sourceforge.net/svnroot/fail2ban/branches/FAIL2BAN-0_8@784 a942ae1a-1317-0410-a47c-b1dcaea8d605

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.
 #
@@ -301,6 +305,8 @@ class Action:
 	#@staticmethod
 	def executeCmd(realCmd):
 		logSys.debug(realCmd)
+		_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)
@@ -312,6 +318,8 @@ class Action:
 					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)