Description of problem:
When a user confined with SELinux to the user_u context, you are unable to log into XFCE.

Version-Release number of selected component (if applicable):
xfce4-session-4.10.0-4.fc18.x86_64

How reproducible:
Always

Steps to Reproduce:
1. Create a user confined as user_u on Fedora 18.
2. Log out as current user and attempt to log back in as confined user.
  
Actual results:
Screen blanks for a second and you end up back at the login screen.

Expected results:

Log in to the system normally.

Additional info:

Linux localhost.localdomain 3.7.4-204.fc18.x86_64 #1 SMP Wed Jan 23 16:44:29 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux

rpm -qa | grep -i selinux
selinux-policy-doc-3.11.1-73.fc18.noarch
selinux-policy-3.11.1-73.fc18.noarch
selinux-policy-targeted-3.11.1-73.fc18.noarch
selinux-policy-devel-3.11.1-73.fc18.noarch
libselinux-python-2.1.12-7.fc18.x86_64
libselinux-2.1.12-7.fc18.x86_64
libselinux-utils-2.1.12-7.fc18.x86_64

SELinux denial:

type=AVC msg=audit(1359602429.970:323): avc:  denied  { sigchld } for  pid=1163 comm="lightdm" scontext=user_u:user_r:user_ssh_agent_t:s0 tcontext=system_u:system_r:xdm_t:s0-s0:c0.c1023 tclass=process

*There's a few things going on here.  The first thing is the being kicked out and not logging in.  The other issue is that there is no error message (for example "Access Denied") or anything before being punted back to the desktop manager.