Description of problem:

If I have invalid sudoers line in nsswitch.conf, I see failures that aren't very descriptive when I run "sudo -l".

Scenario 1:

sudoers: files sss: sudoers: files sss

[root@ibm-x3250m4-02 ~]# sudo -l
Segmentation fault (core dumped)

Scenario 2:

sudoers: files sss: sudoers: files

[root@ibm-x3250m4-02 ~]# vi /etc/nsswitch.conf
[root@ibm-x3250m4-02 ~]# sudo -l
sudo: >>> /etc/sudoers: /etc/sudoers.d: Too many open files near line 117 <<<
sudo: parse error in /etc/sudoers near line 117
sudo: unable to open /etc/sudoers: Too many open files
sudo: unable to open /etc/sudoers: Too many open files
sudo: unable to open /etc/sudoers: Too many open files
sudo: unable to open /etc/sudoers: Too many open files

... seems to continue indefinitely.

Version-Release number of selected component (if applicable):
sudo-1.8.6p3-15.el6.x86_64

How reproducible:
very

Steps to Reproduce:
1.  echo "sudoers: files sss: sudoers: files sss" >> /etc/nsswitch.conf
2.  sudo -l
3.  sed -i '/sudoers/d' /etc/nsswitch.conf
4.  echo "sudoers: files sss: sudoers: files" >> /etc/nsswitch.conf
5.  sudo -l
6.  in another window killall -9 sudo

Actual results:
2. core dump 
5. infinite loop showing error.

Expected results:
Better error messages and no infinite loop.

Additional info: