Description of problem:
Was trying to login with ldap users who had local home directories, but nothing else was local.

Login on virtual terminals worked, but gdm logins fails. After much investigation by rstrode, it was determined that there was no shell being set, and therefore sent, in Xsession.

Lack of default shell should default to /bin/sh, not send nothing at all and cause gdm logins to fail, at least based on passwd(5):

              shell     the program to run at login (if empty,  use  /bin/sh).
                        If  set to a non-existing executable, the user will be
                        unable to login through login(1).

I'm not yet sure if I should also open a gdm bug to suggest that it should correctly handle a lack of shell information being sent.

Version-Release number of selected component (if applicable):
xorg-x11-xinit-1.0.2-15.el5

How reproducible:
Always, if you have a user with no shell (I suspect this would happen if local, as well)

Steps to Reproduce:
1. Set up a user with no shell specified.
2. Try to log into gdm
  
Actual results:
It'll fail with _weird_ errors.

Expected results:
Should work.

Additional info: