Bug#949698: elogind: deletes users’ files under /dev/shm/ on logout

[Thorsten Glaser]

Package: elogind
Version: 241.3-1+debian2
Severity: critical
Justification: breaks unrelated software

I’m using a scheme in which I store ssh-agent and gpg-agent information
across all logins (local X session or ssh or xrdp) under /dev/shm/ since
I needed space that an unprivileged user can use and that doesn’t persist
across reboots.

Since installing elogind, logging out from SSH sessions then on again
both breaks gpg-agent as well as makes ssh-agent instances multiply and,
thus, lose their loaded keys to the user.

Tons of searching and debugging eventuall led me, with strace as root on
it, to the culprit: elogind

lrwxrwxrwx 1 root root 0 Jan 23 20:21 /proc/3061/exe -> /lib/elogind/elogind*

3061  unlinkat(22, "info2", 0)          = 0
3061  unlinkat(21, ".ssh-2339", AT_REMOVEDIR) = 0


Cease that instantly. This breaks unrelated software on the system,
considering that the user’s processes are still running, even if they
logged out from all ssh sessions. In particular, this will also break
software that runs as the user, dæmonised, that uses shared memory.

If you have to clean up after yourselves, keep a list and track of the
files you created and will later need to delete.

It might be a good idea to see whether systemd does the same and, if
so, clone this bugreport and assign the clone to them. I’m not running
systemd, so I can’t do that myself easily.

-- System Information:
Debian Release: bullseye/sid
  APT prefers unreleased
  APT policy: (500, 'unreleased'), (500, 'buildd-unstable'), (500, 'unstable'), (100, 'experimental')
Architecture: x32 (x86_64)
Foreign Architectures: i386, amd64

Kernel: Linux 5.4.0-2-amd64 (SMP w/4 CPU cores)
Kernel taint flags: TAINT_FIRMWARE_WORKAROUND
Locale: LANG=C, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=C (charmap=UTF-8)
Shell: /bin/sh linked to /bin/lksh
Init: sysvinit (via /sbin/init)

Versions of packages elogind depends on:
ii  dbus         1.12.16-2
ii  debconf      1.5.73
ii  libacl1      2.2.53-5
ii  libc6        2.29-9
ii  libcap2      1:2.27-1
ii  libelogind0  241.3-1+debian2
ii  libselinux1  3.0-1
ii  libudev1     244-3
ii  lsb-base     11.1.0

Versions of packages elogind recommends:
ii  libpam-elogind  241.3-1+debian2
ii  policykit-1     0.105-26

elogind suggests no packages.

-- no debconf information