Cloning to RHEL 6.  I also have to wonder if the Common Criteria folks might be interested in this one, since they run /tmp with noexec mount option, and the use of nwfilter seems useful to lock down guests; although failure to run nwfilter is not a security hole, per se.

+++ This bug was initially created as a clone of Bug #752254 +++

Description of problem:

When /tmp filesystem is mounted with noexec option:

tmpfs on /tmp type tmpfs (rw,noexec,nosuid,size=512M)

libvirt fails to initialize nwfilter framework and then fails to start any domain using nwfilter rules.

22:22:32.545: 7699: debug : ebiptablesExecCLI:2590 : cmd='/sbin/ebtables -t nat -L'
eval res=\$\("${cmd}"\)
if [ $? -ne 0 ]; then  echo "Failure to execute command '${cmd}'.";  exit 1;fi

22:22:32.545: 7699: debug : virRunWithHook:833 : /tmp/virtduqjigQ
22:22:32.549: 7699: debug : virRunWithHook:851 : Command stderr: 22:22:32.548: 7733: info : libvirt version: 0.8.7, package: 18.el6_1.1 (Unknown, 2011-09-01-11:22:40, sl6.fnal.gov)
22:22:32.548: 7733: error : __virExec:676 : cannot execute binary /tmp/virtduqjigQ: Permission denied
libvir: error : cannot execute binary /tmp/virtduqjigQ: Permission denied

22:22:32.549: 7699: debug : ebiptablesExecCLI:2611 : rc = 0, status = 1

I have seen similar problems over the internet, and it seems these problems were incorrectly classified as iptables/ip6tables/ebtables not being available in PATH.

Version-Release number of selected component (if applicable):
libvirt-0.8.7-18.el6_1.1.x86_64

(but as far as I can tell after looking at 0.9.7 sources the same problem persists in this version too)

How reproducible:

Mount /tmp with noexec option, restart libvirt.
  
Actual results:

1. Nwfilter not being initialized at libvirt's start:

Nov  8 22:20:48 kastor libvirtd: 22:20:48.984: 7523: info : libvirt version: 0.8.7, package: 18.el6_1.1 (Unknown, 2011-09-01-11:22:40, sl6.fnal.gov)
Nov  8 22:20:48 kastor libvirtd: 22:20:48.994: 7523: info : networkReloadIptablesRules:1382 : Reloading iptables rules
Nov  8 22:20:49 kastor libvirtd: 22:20:49.231: 7523: error : ebiptablesDriverInit:3766 : internal error firewall tools were not found or cannot be used

2. Nwfilter not being usable within domain configuration:

[root@kastor ~]# virsh start av
error: Failed to start domain av
error: internal error Could not get access to ACL tech driver 'ebiptables'

[root@kastor ~]#

Additional info:
Since ebiptablesExecCLI() function's only purpose is to run script generated for checking iptables/ip6tables/ebtables capabilities it should be easy to fix this function. It should invoke this script with `/bin/sh /tmp/tmp_script_path' instead of calling it directly.

--- Additional comment from eblake on 2011-11-08 16:32:20 MST ---

(In reply to comment #0)
> Description of problem:
> 
> Additional info:
> Since ebiptablesExecCLI() function's only purpose is to run script generated
> for checking iptables/ip6tables/ebtables capabilities it should be easy to fix
> this function. It should invoke this script with `/bin/sh /tmp/tmp_script_path'
> instead of calling it directly.

Agree - and this should be a fairly easy patch to get approved.