[cut]
Loaded symbols for /lib/libnss_nis.so.2
Reading symbols from /lib/libnss_files.so.2...done.
Loaded symbols for /lib/libnss_files.so.2
Core was generated by `-:0         '.
Program terminated with signal 11, Segmentation fault.
[New process 2393]
#0  0xb7bf9dd9 in vfprintf () from /lib/libc.so.6
(gdb) where
#0  0xb7bf9dd9 in vfprintf () from /lib/libc.so.6
#1  0xb7cbc6c9 in __vfprintf_chk () from /lib/libc.so.6
#2  0xb7c9e486 in __vsyslog_chk () from /lib/libc.so.6
#3  0xb7c9e8e7 in __syslog_chk () from /lib/libc.so.6
#4  0xb7f7b41a in GreetUser (d=0x8068598, dpy=0xbfd7fddc, verify=0x8060d48, greet=0x8060d30, dlfuncs=0x80608e0) at /usr/include/bits/syslog.h:32
#5  0x08053b96 in ManageSession (d=0x8068598) at session.c:320
#6  0x080506b0 in StartDisplay (d=0x8068598) at dm.c:762
#7  0x0804fbdc in ForEachDisplay (f=0x805079e <CheckDisplayStatus>) at dpylist.c:54
#8  0x08051267 in main (argc=1, argv=0xbfd803a4) at dm.c:630
Current language:  auto; currently asm
(gdb) bt full
#0  0xb7bf9dd9 in vfprintf () from /lib/libc.so.6
No locals.
#1  0xb7cbc6c9 in __vfprintf_chk () from /lib/libc.so.6
No locals.
#2  0xb7c9e486 in __vsyslog_chk () from /lib/libc.so.6
No locals.
#3  0xb7c9e8e7 in __syslog_chk () from /lib/libc.so.6
No locals.
#4  0xb7f7b41a in GreetUser (d=0x8068598, dpy=0xbfd7fddc, verify=0x8060d48, greet=0x8060d30, dlfuncs=0x80608e0) at /usr/include/bits/syslog.h:32
        pam_error = 7
        pcd = {d = 0x8068598, greet = 0x8060d30, username_display = 0x0}
        username = 0x1 <Address 0x1 out of bounds>
        login_prompt = <value optimized out>
        pamhp = (pam_handle_t **) 0x8060d28
        pc = {conv = 0xb7f7bcf6 <pamconv>, appdata_ptr = 0xbfd7fd2c}
        pam_fname = <value optimized out>
        i = 134665472
#5  0x08053b96 in ManageSession (d=0x8068598) at session.c:320
        pid = 0
        dpy = (Display *) 0x806fa10
        greet_stat = <value optimized out>
        greet_user_proc = (GreetUserProc) 0xb7f7af98 <GreetUser>
        greet_lib_handle = (void *) 0x806d500
#6  0x080506b0 in StartDisplay (d=0x8068598) at dm.c:762
No locals.
#7  0x0804fbdc in ForEachDisplay (f=0x805079e <CheckDisplayStatus>) at dpylist.c:54
        d = (struct display *) 0x1
        next = (struct display *) 0x0
#8  0x08051267 in main (argc=1, argv=0xbfd803a4) at dm.c:630
        oldpid = <value optimized out>
        oldumask = 1
        cmdbuf = "/bin/rm -f /var/lib/xdm/authdir/authfiles/A*\000\000\000\000?\027? ??\000\000\000\000\001\000\000\000\224?????\210???\000?\b\001?\000\000\000\000?/?\001\000\000\000?\022?????\000??\000?\2042?m&?p\n?\001\000\000\000\000\020?\000??\000\000\000\000\000\000\000\000?/?p\n?\233\021?\001\000\000\0000=? ??\000\000\000\000\001\000\000\000\210:?@U?p\n??\000?\000\000\000\000\000\000\000\000"...
(gdb)