Bug#970534: systemd: `busctl introspect org.freedesktop.login1 /org/freedesktop/login1` fails

[Ansgar]

Package: systemd
Version: 246.5-1
Severity: normal
File: /usr/bin/busctl
Tags: upstream

The following command fails (as a regular user):

+---
| $ busctl introspect org.freedesktop.login1 /org/freedesktop/login1
| Failed to get all properties on interface org.freedesktop.login1.Manager: Input/output error
+---

Other things work as expected, for example:

    busctl introspect org.freedesktop.login1 /org/freedesktop/login1/user/_1000

lists four interfaces with methods, signals and properties as
expected: org.freedesktop.DBus.Introspectable,
org.freedesktop.DBus.Peer, org.freedesktop.DBus.Properties,
org.freedesktop.login1.User.

d-feet also shows the interface, but it doesn't show property values.
I tried requesting all property values in d-feet and one failed:
`BootLoaderEntries` of the `org.freedesktop.login1.Manager` couldn't
be retrieved by d-feet and showed this error in the terminal window:

+---
| Traceback (most recent call last):
|   File "/usr/lib/python3/dist-packages/dfeet/introspection.py", line 114, in __treeview_row_activated_cb
|     result = proxy.call_sync("Get", args, 0, -1, None)
| gi.repository.GLib.Error: g-dbus-error-quark: GDBus.Error:org.freedesktop.DBus.Error.IOError: Input/output error (5)
+---

I guess `busctl` encounters the same error.  Instead of displaying
only an error, it should probably show as much as it could and some
marker do indicate some values couldn't be retrieved.

Ansgar

-- Package-specific info:

-- System Information:
Debian Release: bullseye/sid
  APT prefers unstable-debug
  APT policy: (500, 'unstable-debug'), (500, 'testing-debug'), (500, 'testing'), (500, 'stable'), (300, 'buildd-unstable'), (300, 'unstable'), (1, 'experimental-debug'), (1, 'buildd-experimental'), (1, 'experimental')
Architecture: amd64 (x86_64)

Kernel: Linux 5.8.0-1-amd64 (SMP w/8 CPU threads)
Kernel taint flags: TAINT_PROPRIETARY_MODULE, TAINT_OOT_MODULE, TAINT_UNSIGNED_MODULE
Locale: LANG=C, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages systemd depends on:
ii  adduser                          3.118
ii  libacl1                          2.2.53-8
ii  libapparmor1                     2.13.4-3
ii  libaudit1                        1:2.8.5-3+b1
ii  libblkid1                        2.36-3
ii  libc6                            2.31-3
ii  libcap2                          1:2.43-1
ii  libcrypt1                        1:4.4.17-1
ii  libcryptsetup12                  2:2.3.4-1
ii  libgcrypt20                      1.8.6-2
ii  libgnutls30                      3.6.14-2+b1
ii  libgpg-error0                    1.38-2
ii  libidn2-0                        2.3.0-1
ii  libip4tc2                        1.8.5-3
ii  libkmod2                         27+20200310-2
ii  liblz4-1                         1.9.2-2
ii  liblzma5                         5.2.4-1+b1
ii  libmount1                        2.36-3
ii  libpam0g                         1.3.1-5
ii  libpcre2-8-0                     10.34-7
ii  libseccomp2                      2.4.3-1+b1
ii  libselinux1                      3.1-2
ii  libsystemd0                      246.5-1
ii  libzstd1                         1.4.5+dfsg-4
ii  mount                            2.36-3
ii  systemd-timesyncd [time-daemon]  246.5-1
ii  util-linux                       2.36-3

Versions of packages systemd recommends:
ii  dbus  1.12.20-1

Versions of packages systemd suggests:
ii  policykit-1        0.105-29
ii  systemd-container  246.5-1

Versions of packages systemd is related to:
ii  dracut           050+65-1
pn  initramfs-tools  <none>
pn  libnss-systemd   <none>
ii  libpam-systemd   246.5-1
ii  udev             246.5-1

-- no debconf information