Description of problem:
The su command segfaults if I configure PAM to authenticate using Kerberos and
provide an incorrect password.

Version-Release number of selected component (if applicable):
coreutils-5.97-11

How reproducible:
Every time

Steps to Reproduce:
1. Configure PAM as below.
2. su - someuser
3. Enter an incorrect password
  
Actual results:
Segmentation fault

Expected results:
The su utility should refuse to authenticate user and not segfault.

Additional info:
auth        required      /lib/security/$ISA/pam_env.so
auth        optional      /lib/security/$ISA/pam_keyring.so
auth        sufficient    /lib/security/$ISA/pam_unix.so use_first_pass
auth        [authinfo_unavail=ignore success=1 default=2]
/lib/security/$ISA/pam_krb5.so use_first_pass
auth        required      /lib/security/$ISA/pam_deny.so
[...]

If I remove the line for pam_krb5.so then su will not segfault.

(gdb) run - mike
Starting program: /bin/su - mike
[Thread debugging using libthread_db enabled]
[New Thread 805494224 (LWP 2555)]
Error while reading shared library symbols:
Cannot find new threads: generic error
Password: 

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 805494224 (LWP 2555)]
0x07fd60d0 in _pam_dispatch () from /lib/libpam.so.0
(gdb) ba
#0  0x07fd60d0 in _pam_dispatch () from /lib/libpam.so.0
#1  0x07fd55d8 in pam_authenticate () from /lib/libpam.so.0
#2  0x08003838 in main (argc=3, argv=0x7f8d54b4) at su.c:364
#3  0x07dc0d4c in generic_start_main () from /lib/libc.so.6
#4  0x07dc0f74 in __libc_start_main () from /lib/libc.so.6
#5  0x00000000 in ?? ()
(gdb)