[SOLVED] No longer able to log in from TTY with numeric username

polm23 · 2022-04-08 05:48:41

(Sorry if this is the wrong board, wasn't really sure where this belonged.)

I ran pacman -Syu on my main Arch system after a month or two (slow, I know) and had some trouble after rebooting. I usually log in from a TTY and use startx to start my WM, but after logging in (before I get a prompt) an error would flash on the screen and then I'd be returned to the TTY login.

I was able to capture the error by recording a video of my screen:

Assert from 'close_nointr(fd) != -EBADF' failed at src/basic/fd-util.c:74, function safe_close(). Aborting.

At first I thought maybe something in my bashrc or profile was an issue, so I used a blank one, but without success. Then it occurred to me it might be username related, so I tried creating some new users and found the issue seems to only affect purely numeric usernames (like 23 or 42). I am not familiar with the function in the error but it looks like maybe the username is being interpreted as a file descriptor.

I realize that using a numeric username is technically a bad idea and in theory opens up a can of worms for no benefit; I do it just out of vanity. But honestly after a decade of doing it this is the first time I've run into any issues related to logging in.

At the moment I am able to log in as root and su to my usual user, but it would be great if I could fix this. Also treating usernames as file descriptors suggests the potential for bugs elsewhere. Based on journalctl it looks like my login process is dumping core, details:

Module linux-vdso.so.1 with build-id ae8518a0710c2679844504efb751b01abf13cef5
Module libnss_systemd.so.2 with build-id aa54bea74fb4d938f92ea6452d93d1f00201a8a0
Module pam_warn.so with build-id 5b73faf8abe96fd6b460ef6c703cb127fe8e312b
Module pam_deny.so with build-id 023269774049f20683b13e4304d7e254a1c7a0b2
Module pam_systemd.so with build-id 926ebe98215dd68688283b4d29461e6b1fb91006
Module pam_mail.so with build-id 2e76a4a0eb21f3217a766329838b850a7085b16b
Module pam_motd.so with build-id f3ed720bd88c652152737c440039dd0b9589174c
Module pam_limits.so with build-id 904f399db1e3e4b168ab6fcd9152c52a52d41d3f
Module pam_keyinit.so with build-id 6bd2a336d004dc8458f1c4cdf8fcd941d1c4925f
Module pam_loginuid.so with build-id 45bcbb167aef0cae946704ce218c4a8f442393ad
Module pam_time.so with build-id 27045c468605f64203a35fa2d83d7c423220c298
Module pam_access.so with build-id 9e188fc5620336bf5919f51c25952325ff4de10e
Module pam_env.so with build-id e28d502d7e4820f936437d20d459e51036d1a243
Module pam_permit.so with build-id 59f4a785cc0a8400f0438321eac923ff96c34bdd
Module libresolv.so.2 with build-id 46ffdf3d477a170314060c26927470d7399bc900
Module libkeyutils.so.1 with build-id ac405ddd17be10ce538da3211415ee50c8f8df79
Module libkrb5support.so.0 with build-id 36db7c21bc57a9b934ad2d3463782db9fef4af07
Module libcom_err.so.2 with build-id 358b783c9b3d12ba8248519ea2e7f3da4c4e0297
Module libk5crypto.so.3 with build-id f1c113fea46023cdf62c7e51cb643c45831abdd5
Module libkrb5.so.3 with build-id 9350783c946d77aec8ee8fd9c6bc12f4f7b72be9
Module libpthread.so.0 with build-id 7fa8b52fae071a370ba4ca32bf9490a30aff31c4
Module libgssapi_krb5.so.2 with build-id 1813217c8baf82a1078772eed0d868310cd59f8b
Module libtirpc.so.3 with build-id 5bef2adfdee3df283f593b3e2d37b6dac405256a
Module libcrypt.so.2 with build-id a0a45f81771945f0559d04e93726d245159930da
Module pam_unix.so with build-id 608e03b3693ba42760a2b836763d41d1c079a2bf
Module libgcc_s.so.1 with build-id 5d817452a709ca3a213341555ddcf446ecee37fa
Module libm.so.6 with build-id 596b63a006a4386dcab30912d2b54a7a61827b07
Module libcap.so.2 with build-id eb6dae97527fc89dbb0d5bb581a15acd02ae9f56
Module pam_systemd_home.so with build-id d12a24c451a7d1dc2cb1dc953f8041d28cafbaba
Module pam_faillock.so with build-id 7e42bd70303fbc079e452d777b6907bb5614df5d
Module pam_shells.so with build-id 827b2de32a5ec108462699009e6e441b42792b26
Module pam_nologin.so with build-id 9f749b8e7bd55bfb75e294bc32aaa56ac353d6c0
Module pam_securetty.so with build-id f50f4594f4bc962c6e9b8d75b3219dfb610f27d1
Module libcap-ng.so.0 with build-id 09690c43af29ef92bbec2e53e29101b2b8e9c48c
Module ld-linux-x86-64.so.2 with build-id c09c6f50f6bcec73c64a0b4be77eadb8f7202410
Module libdl.so.2 with build-id bb9bd2657bfba9f60bd34d2050cc63a7eb024bc4
Module libaudit.so.1 with build-id 27ca9470fd239e2f61c83e293f24f266789485b6
Module libc.so.6 with build-id 85766e9d8458b16e9c7ce6e07c712c02b8471dbc
Module libpam_misc.so.0 with build-id 74aaf2951cb6eb6cf89a69339285a6015876bee4
Module libpam.so.0 with build-id bb11b2685fe89555938ffd330ea44d82b0f8701c
Module login with build-id cf05f4e8b1b90fcc6fefe422748d91003165b80a
Stack trace of thread 1504:
#0  0x00007f27e0ef134c __pthread_kill_implementation (libc.so.6 + 0x8f34c)
#1  0x00007f27e0ea44b8 raise (libc.so.6 + 0x424b8)
#2  0x00007f27e0e8e534 abort (libc.so.6 + 0x2c534)
#3  0x00007f27e0de34e8 n/a (pam_systemd_home.so + 0x2b4e8)
#4  0x00007f27e0de3cff n/a (pam_systemd_home.so + 0x2bcff)
#5  0x00007f27e0dd5340 n/a (pam_systemd_home.so + 0x1d340)
#6  0x00007f27e0dd993b n/a (pam_systemd_home.so + 0x2193b)
#7  0x00007f27e107447c n/a (libpam.so.0 + 0x347c)
#8  0x00007f27e1074fe2 pam_end (libpam.so.0 + 0x3fe2)
#9  0x0000564cd5030061 n/a (login + 0x5061)
#10 0x00007f27e0e8f310 __libc_start_call_main (libc.so.6 + 0x2d310)
#11 0x00007f27e0e8f3c1 __libc_start_main@@GLIBC_2.34 (libc.so.6 + 0x2d3c1)
#12 0x0000564cd5030ad5 n/a (login + 0x5ad5)
ELF object binary architecture: AMD x86-64

Is this a bug I should report somewhere, or is there a change I can read about somewhere?

Last edited by polm23 (2022-04-11 04:46:51)

seth · 2022-04-08 06:32:33

#3 0x00007f27e0de34e8 n/a (pam_systemd_home.so + 0x2b4e8)

Unless you intend to use this "feature", you can just remove the homed pam from /etc/pam.d/system-auth
Since it's optional (leading "-") you can also probably (haven't tried, be sure to be able to fix this offline) remove /usr/lib/security/pam_systemd_home.so and block it it your pacman.conf

Pure numeric usernames are in fact a bad idea (and prohibited by the default $NAME_REGEX), but technically POSIX complaint (even the leading hyphen is something you "should"™ not do, but is not strongly prohibited.
https://pubs.opengroup.org/onlinepubs/9 … tag_03_437
https://pubs.opengroup.org/onlinepubs/9 … tag_03_282

polm23 · 2022-04-10 15:31:57

Thanks for the quick answer! I am definitely not intentionally using that.

Unfortunately I've never worked with pam.d files. When you say to remove the pam from system-auth, what do you mean? I tried commenting the line or changing the condition to "optional" but neither seemed to have any effect. I haven't tried fiddling with the .so yet.

I am confused as to why that module is doing anything at all by default. I checked the systemd service for it and it's disabled. I guess this is just systemd being systemd?

polm23 · 2022-04-10 15:36:26

Never mind - I was only commenting out the first pam_systemd_home line. I didn't realize there were four or five of them in the file. After commenting them all out login works like it did before.

Thanks again for your help!

seth · 2022-04-10 15:43:50

Commenting the lines (there're 4) should™ do, "optional" won't help since you're still optionally running the module (causing the crash)
"pam_systemd_home.so" should™ then no longer appear in any backtraces or anywhere.

Edit: fuck.
Edit #2: Please always remember to mark resolved threads by editing your initial posts subject - so others will know that there's no task left, but maybe a solution to find.
Thanks.

Last edited by seth (2022-04-10 15:44:55)

polm23 · 2022-04-11 04:47:13

Sorry for the extra reply there, and subject edited. Thanks again!

Arch Linux

#1 2022-04-08 05:48:41

[SOLVED] No longer able to log in from TTY with numeric username

#2 2022-04-08 06:32:33

Re: [SOLVED] No longer able to log in from TTY with numeric username

#3 2022-04-10 15:31:57

Re: [SOLVED] No longer able to log in from TTY with numeric username

#4 2022-04-10 15:36:26

Re: [SOLVED] No longer able to log in from TTY with numeric username

#5 2022-04-10 15:43:50

Re: [SOLVED] No longer able to log in from TTY with numeric username

#6 2022-04-11 04:47:13

Re: [SOLVED] No longer able to log in from TTY with numeric username

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