Hi all, (Cc:ing Russel Stuart, the maintainer and upstream author of libpam-python)
On Do 04 Sep 2014 20:24:43 CEST, Petter Reinholdtsen wrote:
Package: libpam-mklocaluser Version: 0.10 Severity: important User: debian-edu@lists.debian.org Usertags: debian-edu When logging in a LDAP user into kdm for the first time on a freshly installed Roaming Workstation based on Debian Edu Jessie, the login went fine but instead of being told that a local user was created, I was told that the user had no home directory and the login failed. These are the related messages in /var/log/auth.log:Sep 4 19:32:08 thinkpadx200 kdm: :0[2256]: pam_unix(kdm:auth): authentication failure; logname= uid=0 euid=0 tty=:0 ruser= rhost= user=pereSep 4 19:32:08 thinkpadx200 kdm: :0[2256]: pam_sss(kdm:auth): authentication success; logname= uid=0 euid=0 tty=:0 ruser= rhost= user=pereSep 4 19:32:08 thinkpadx200 kdm: :0[2256]: pam_unix(kdm:session): session opened for user pere by (uid=0) Sep 4 19:32:08 thinkpadx200 systemd-logind[1735]: New session 1 of user pere. Sep 4 19:32:08 thinkpadx200 systemd-logind[1735]: Linked /tmp/.X11-unix/X0 to /run/user/1000/X11-display. Sep 4 19:32:08 thinkpadx200 systemd: pam_unix(systemd-user:session): session opened for user pere by (uid=0)Sep 4 19:32:08 thinkpadx200 pam_mklocaluser[3283]: Creating local passwd/shadow entry uid=1000(pere) gid=1000(pere) gecos='Petter Reinholdtsen' home=/home/pereSep 4 19:32:08 thinkpadx200 pam_mklocaluser[3283]: Creating local home directory for user 'pere' Sep 4 19:32:08 thinkpadx200 pam_mklocaluser[2256]: pam_ck_connector(kdm:session): nox11 mode, ignoring PAM_TTY :0Sep 4 19:32:08 thinkpadx200 pam_mklocaluser[3283]: Failure while creating local user: Conversation error Sep 4 19:32:08 thinkpadx200 pam_mklocaluser[3283]: pam_ck_connector(systemd-user:session): cannot determine display-deviceSep 4 19:33:11 thinkpadx200 kdm: :0[2256]: pam_unix(kdm:session): session closed for user pereSep 4 19:33:17 thinkpadx200 systemd-logind[1735]: Removed session 1. The new user is present in /etc/passwd and /etc/shadow, so I expect the python script crashed when trying to send a message back to kdm, but it could have happend earlier too. The mklocaluser.d/ fragment in place seem to have executed as it should (~pere/.local/share/user-places.xbel is correct). syslog.syslog("Creating local home directory for user '%s'" % user) # Copy content of /etc/skel shutil.copytree("/etc/skel/.", newhomedir, True) # Change perm of new home dir os.chmod(newhomedir, dirmode) chown_recursive(newhomedir, uid, gid) # Flush nscd cache to get rid of original user entry if os.access("/usr/sbin/nscd", os.X_OK): runcmd(pamh, "/usr/sbin/nscd -i passwd") # Hook for adjusting the freshly created home directory # FIXME Should be rewritten in python, I guessruncmd(pamh, "if [ -d /etc/mklocaluser.d ]; then ORIGHOMEDIR='%s' USER='%s' /bin/run-parts /etc/mklocaluser.d ; fi" % (homedir, user))# Let the user know what is going on msg = pamh.Message(pamh.PAM_TEXT_INFO,"Local user created in /home/, please log in again to start using it.")pamh.conversation(msg) # Throw out user, as the log process cached the home directory # and need to be restarted. return pamh.PAM_TRY_AGAIN No idea what could go wrong here.
I tracked this issue down a bit further today. The bug still exists on Debian buster based Debian Edu Roaming Workstation systems utilizing libpam-mklocaluser (being a Python script for libpam-python).
I tested this with LightDM and what I see is LightDM segfaulting in pam_python.so:
```Feb 19 11:58:12 test-fai-installation kernel: [ 6682.762317] lightdm[31521]: segfault at 8 ip 00007f3bf0fed5f0 sp 00007ffde4d13110 error 4 in pam_python.so[7f3bf0feb000+4000]
```
This happens during the pamh.conversation() call:
```
msg = pamh.Message(pamh.PAM_TEXT_INFO,
"Local user created in /home/, please log in
again to start using it.")
pamh.conversation(msg)
```
The pam_python.so module simply crashes without emitting a Python
exception or anything (I tried to wrap it into a try: ... except
pamh.exception: ... block).
When attaching a gdb to the correct LightDM process (one of the two "lightdm --session-child" processes), I do get the following backtrace:
``` Thread 1 "lightdm" received signal SIGSEGV, Segmentation fault. [Switching to Thread 0x7f7110741880 (LWP 20800)]0x00007f711045b5f0 in PamHandle_conversation (self=0x7f710dcb37a0, args=<optimized out>, kwds=<optimized out>) at pam_python.c:1899
1899 pam_python.c: Datei oder Verzeichnis nicht gefunden. (gdb) bt full#0 0x00007f711045b5f0 in PamHandle_conversation (self=0x7f710dcb37a0, args=<optimized out>, kwds=<optimized out>) at pam_python.c:1899
err = <optimized out>
pamHandle = 0x7f710dcb37a0
prompts = 0x7f710d863a50
result_tuple = 0x0
message_array = 0x563f19187850
message_vector = 0x563f191afa00
response_array = 0x0
result = 0x0
response = 0x0
conv = 0x563f190fd430
prompt_count = <optimized out>
i = <optimized out>
pam_result = <optimized out>
prompts_is_sequence = 0
py_result = <optimized out>
kwlist = {0x7f711045d42a "prompts", 0x0}
#1 0x00007f71101a8f80 in PyEval_EvalFrameEx () at
/lib/x86_64-linux-gnu/libpython2.7.so.1.0
#2 0x00007f71101a8540 in PyEval_EvalFrameEx () at
/lib/x86_64-linux-gnu/libpython2.7.so.1.0
#3 0x00007f71101a0852 in PyEval_EvalCodeEx () at
/lib/x86_64-linux-gnu/libpython2.7.so.1.0
#4 0x00007f711022747c in () at /lib/x86_64-linux-gnu/libpython2.7.so.1.0#5 0x00007f7110251dd3 in PyObject_Call () at /lib/x86_64-linux-gnu/libpython2.7.so.1.0 #6 0x00007f711019fef7 in PyEval_CallObjectWithKeywords () at /lib/x86_64-linux-gnu/libpython2.7.so.1.0
#7 0x00007f711045bb70 in call_python_handler(result=result@entry=0x7ffe20a685d8, pamHandle=0x7f710dcb37a0, handler_function=handler_function@entry=0x7f710d874668, handler_name=handler_name@entry=0x7f711045d3f0 "pam_sm_open_session", flags=flags@entry=0, argc=argc@entry=2, argv=0x563f1910ac20) at pam_python.c:2752
arg_object = 0x0
argv_object = 0x7f710d96a6c8
flags_object = 0x563f19151ca0
handler_args = 0x7f710d8bfeb0
py_resultobj = 0x0
i = <optimized out>
pam_result = <optimized out>
#8 0x00007f711045c445 in call_handler (handler_name=0x7f711045d3f0
"pam_sm_open_session", pamh=<optimized out>, flags=0, argc=2,
argv=0x563f1910ac20)
at pam_python.c:2803
handler_function = 0x7f710d874668
pamHandle = 0x7f710dcb37a0
py_resultobj = 0x0
pam_result = 0
#9 0x00007f711112ad14 in _pam_dispatch_aux
(use_cached_chain=<optimized out>, resumed=<optimized out>,
h=0x563f1910c8f0, flags=0, pamh=0x563f190fe860)
at pam_dispatch.c:110
retval = <optimized out>
cached_retval = <optimized out>
action = <optimized out>
depth = <optimized out>
status = 0
prev_level = <optimized out>
stack_level = <optimized out>
impression = 1
skip_depth = 0
substates = 0x563f191343e0
h = 0x563f19100930
retval = <optimized out>
use_cached_chain = <optimized out>
resumed = <optimized out>
#10 0x00007f711112ad14 in _pam_dispatch (pamh=0x563f190fe860,
flags=flags@entry=0, choice=choice@entry=4) at pam_dispatch.c:411
h = 0x563f19100930
retval = <optimized out>
use_cached_chain = <optimized out>
resumed = <optimized out>
#11 0x00007f711112f755 in pam_open_session (pamh=<optimized out>,
flags=flags@entry=0) at pam_session.c:23
#12 0x0000563f18952d38 in session_child_run (argc=<optimized out>,
argv=<optimized out>) at session-child.c:535
fd = <optimized out>
version = 3
service = 0x563f190fd370 "lightdm"
username = 0x563f190fd390 "gabmik"
unused_class = 0x0
tty = 0x563f190fd3b0 "/dev/tty7"
remote_host_name = 0x0
xdisplay = 0x563f190fd3d0 ":0"
x_authority = 0x563f191187a0
conversation = {conv = 0x563f18952300 <pam_conv_cb>,
appdata_ptr = 0x0}
result = <optimized out>
authentication_result = 0
user = 0x7f710800a700
authentication_result_string = 0x563f19135680 "Success"
auth_complete = 1
log_filename = 0x563f191357e0 ".xsession-errors"
log_mode = LOG_MODE_BACKUP_AND_TRUNCATE
x_authority_filename = 0x7f7108005a60
"/skole/tjener/home1/gabmik/.Xauthority"
env_length = 10
command_argc = 2
command_argv = 0x563f19133f90
i = <optimized out>
error = 0x563f190fd410
bus = <optimized out>
login1_session_id = <optimized out>
console_kit_cookie = <optimized out>
uid = <optimized out>
gid = <optimized out>
home_directory = <optimized out>
return_code = <optimized out>
#13 0x0000563f1893c5a9 in main (argc=<optimized out>, argv=<optimized
out>) at lightdm.c:562
action =
{__sigaction_handler = {sa_handler = 0x1, sa_sigaction =
0x1}, sa_mask = {__val = {0 <repeats 16 times>}}, sa_flags =
268435456, sa_restorer = 0x770000007c}
messages = Python Exception <class 'gdb.MemoryError'> Cannot
access memory at address 0x7:
```However, what would be the next steps in testing further things in this segmentation fault?
Greets, Mike -- DAS-NETZWERKTEAM c\o Technik- und Ökologiezentrum Eckernförde Mike Gabriel, Marienthaler str. 17, 24340 Eckernförde mobile: +49 (1520) 1976 148 landline: +49 (4351) 850 8940 GnuPG Fingerprint: 9BFB AEE8 6C0A A5FF BF22 0782 9AF4 6B30 2577 1B31 mail: mike.gabr...@das-netzwerkteam.de, http://das-netzwerkteam.de
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