Description of problem:
When configured to use the "session" function of a PAM module, sudo calls pam_open_session(), but never calls pam_close_session() or pam_end() to close the session.

Version-Release number of selected component (if applicable):
sudo-1.7.4p5-7.el6

How reproducible:
With the code instrumented to show the pid and status of the pamh handle in both places, this is clear:

$ sudo true
** pam_init: pid 24820, pamh is set
** pam_end_session: pid 24819, pamh is null

Steps to Reproduce:
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Actual results:
pam_close_session() or pam_end() are never called to end the session


Expected results:
pam_close_session() or pam_end() are called appropriately

Additional info:
In auth/pam.c, there is this:

static pam_handle_t *pamh;	/* global due to pam_prep_user() */

This defines a static global variable to hold the PAM handle, which is initialized in pam_init(), and should be used in pam_end_session() to end the session. The use of the global variable for coordination is broken, however, because pam_init() is called in a subprocess, whereas pam_end_session() is called later in the parent process; thus, the handle is always NULL when pam_end_session() runs, and sudo never calls the PAM session close method.