SELinux is preventing /usr/lib64/xulrunner-2/plugin-container from 'use' accesses on the fd /dev/null.

*****  Plugin catchall_boolean (80.5 confidence) suggests  *******************

If you want to allow all domains to use other domains file descriptors
Then you must tell SELinux about this by enabling the 'allow_domain_fd_use' boolean.
Do
setsebool -P allow_domain_fd_use 1

*****  Plugin leaks (10.5 confidence) suggests  ******************************

If you want to ignore plugin-container trying to use access the null fd, because you believe it should not need this access.
Then you should report this as a bug.  
You can generate a local policy module to dontaudit this access.
Do
# grep /usr/lib64/xulrunner-2/plugin-container /var/log/audit/audit.log | audit2allow -D -M mypol
# semodule -i mypol.pp

*****  Plugin catchall (10.5 confidence) suggests  ***************************

If you believe that plugin-container should be allowed use access on the null fd by default.
Then you should report this as a bug.
You can generate a local policy module to allow this access.
Do
allow this access for now by executing:
# grep plugin-containe /var/log/audit/audit.log | audit2allow -M mypol
# semodule -i mypol.pp

Additional Information:
Source Context                unconfined_u:unconfined_r:mozilla_plugin_t:s0-s0:c
                              0.c1023
Target Context                unconfined_u:unconfined_r:unconfined_dbusd_t:s0-s0
                              :c0.c1023
Target Objects                /dev/null [ fd ]
Source                        plugin-containe
Source Path                   /usr/lib64/xulrunner-2/plugin-container
Port                          <Inconnu>
Host                          (removed)
Source RPM Packages           xulrunner-2.0.1-2.fc16
Target RPM Packages           
Policy RPM                    selinux-policy-3.9.16-28.fc16
Selinux Enabled               True
Policy Type                   targeted
Enforcing Mode                Enforcing
Host Name                     (removed)
Platform                      Linux (removed) 3.0-0.rc3.git0.3.fc16.x86_64 #1
                              SMP Tue Jun 14 17:13:27 UTC 2011 x86_64 x86_64
Alert Count                   1
First Seen                    mer. 15 juin 2011 21:09:09 CEST
Last Seen                     mer. 15 juin 2011 21:09:09 CEST
Local ID                      56cd4259-8011-4555-a812-4515f052e882

Raw Audit Messages
type=AVC msg=audit(1308164949.499:95): avc:  denied  { use } for  pid=2703 comm="plugin-containe" path="/dev/null" dev=devtmpfs ino=5052 scontext=unconfined_u:unconfined_r:mozilla_plugin_t:s0-s0:c0.c1023 tcontext=unconfined_u:unconfined_r:unconfined_dbusd_t:s0-s0:c0.c1023 tclass=fd


type=AVC msg=audit(1308164949.499:95): avc:  denied  { use } for  pid=2703 comm="plugin-containe" path="/dev/null" dev=devtmpfs ino=5052 scontext=unconfined_u:unconfined_r:mozilla_plugin_t:s0-s0:c0.c1023 tcontext=unconfined_u:unconfined_r:unconfined_dbusd_t:s0-s0:c0.c1023 tclass=fd


type=SYSCALL msg=audit(1308164949.499:95): arch=x86_64 syscall=execve success=yes exit=0 a0=7fcb5800bac8 a1=7fcb5800c210 a2=28f1010 a3=7fcb5f79d6a0 items=0 ppid=2647 pid=2703 auid=500 uid=500 gid=500 euid=500 suid=500 fsuid=500 egid=500 sgid=500 fsgid=500 tty=(none) ses=1 comm=plugin-containe exe=/usr/lib64/xulrunner-2/plugin-container subj=unconfined_u:unconfined_r:mozilla_plugin_t:s0-s0:c0.c1023 key=(null)

Hash: plugin-containe,mozilla_plugin_t,unconfined_dbusd_t,fd,use

audit2allow

#============= mozilla_plugin_t ==============
#!!!! This avc can be allowed using the boolean 'allow_domain_fd_use'

allow mozilla_plugin_t unconfined_dbusd_t:fd use;

audit2allow -R

#============= mozilla_plugin_t ==============
#!!!! This avc can be allowed using the boolean 'allow_domain_fd_use'

allow mozilla_plugin_t unconfined_dbusd_t:fd use;

No idea if it's a policy or firefox bug, looks scarry and should be fixed one way or the other anyway