"machinectl shell" connections immediately terminated

Sorry, the patch in:

https://github.com/systemd/systemd/commit/e8cf09b2a2ad0d48e5493050d54251d5f512d9b6

is already applied in systemd 249.9-0ubuntu2, so that is not the solution.

These are the messages reported by journalctl inside the container:

Jan 29 12:27:53 ns-xxx systemd[153]: Assertion 'a' failed at src/basic/path-util.c:486, function path_compare(). Aborting.
Jan 29 12:27:53 ns-xxx systemd[1]: container-shell@2.service: Succeeded.
-- Subject: Unit succeeded
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
--
-- The unit container-shell@2.service has successfully entered the 'dead' state.

From the last comments in:

https://github.com/systemd/systemd/issues/22234

the problem is due to an incompatibility of the new versions of systemd with older ones.
In fact the container was running ubuntu focal, with systemd_245.4-4ubuntu3.15, and the host was running ubuntu jammy with systemd 249.9-0ubuntu2.
So the problem should be ideally solved by including the patch in:

https://github.com/systemd/systemd/commit/e8cf09b2a2ad0d48e5493050d54251d5f512d9b6

also in older versions of systemd.

Status changed to 'Confirmed' because the bug affects multiple users.

Just tested, and can confirm backporting e8cf09b2a2ad0d48e5493050d54251d5f512d9b6 to focal's systemd fixes the segfaults when using machinectl shell on a Jammy host trying to start a shell in a Focal nspawn container.

Please consider backporting for Focal (20.04) at least. The backport is trivial and applies cleanly as-is except for patch offsets.

Might be wise to test some other combinations though. For example hosts without this commit, running nspawn containers with it.

The commit in question is included in upstream v246+, so only affects Focal.

A fix for this issue has been staged in git for the next Focal SRU: https://git.launchpad.net/~ubuntu-core-dev/ubuntu/+source/systemd/commit/?id=b10c6853050dde26665caf3b15444d768d2bc498

Thank you @enr0n for providing the merge proposal!

Hello renbag, or anyone else affected,

Accepted systemd into focal-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/systemd/245.4-4ubuntu3.18 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, what testing has been performed on the package and change the tag from verification-needed-focal to verification-done-focal. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-focal. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

All autopkgtests for the newly accepted systemd (245.4-4ubuntu3.18) for focal have finished running.
The following regressions have been reported in tests triggered by the package:

linux-gke-5.15/5.15.0-1015.18~20.04.1 (arm64, amd64)
netplan.io/0.104-0ubuntu2~20.04.2 (armhf)
linux-hwe-5.15/5.15.0-48.54~20.04.1 (armhf, amd64)
gvfs/1.44.1-1ubuntu1.1 (ppc64el)
linux-oracle-5.15/5.15.0-1016.20~20.04.1 (arm64)
linux-oracle-5.13/5.13.0-1036.43~20.04.1 (arm64)
linux-hwe-5.11/5.11.0-61.61 (arm64)
systemd/245.4-4ubuntu3.18 (armhf)

Please visit the excuses page listed below and investigate the failures, proceeding afterwards as per the StableReleaseUpdates policy regarding autopkgtest regressions [1].

https://people.canonical.com/~ubuntu-archive/proposed-migration/focal/update_excuses.html#systemd

[1] https://wiki.ubuntu.com/StableReleaseUpdates#Autopkgtest_Regressions

Thank you!

I can't make comments about the regressions, however I tested the systemd (245.4-4ubuntu3.18) package in a focal container and confirm that solves this bug (connecting from a jammy host).

The autopkgtest regressions were all resolved with retries.

I verified this fix as well, using the test plan above to create a focal container with -proposed enabled:

nr@clean-jammy-amd64:~$ lsb_release -cs
jammy
nr@clean-jammy-amd64:~$ sudo machinectl shell test-container
Connected to machine test-container. Press ^] three times within 1s to exit session.
root@clean-jammy-amd64:~# apt-cache policy systemd
systemd:
  Installed: 245.4-4ubuntu3.18
  Candidate: 245.4-4ubuntu3.18
  Version table:
 *** 245.4-4ubuntu3.18 500
        500 http://archive.ubuntu.com/ubuntu focal-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
     245.4-4ubuntu3 500
        500 http://archive.ubuntu.com/ubuntu focal/main amd64 Packages
root@clean-jammy-amd64:~# lsb_release -cs
focal
root@clean-jammy-amd64:~#

> The patch expands the case where the TERM variable is inherited from PID 1 when building an execution environment, e.g. for a container. If problems were to occur, it would be related to the value of TERM in environments forked off of PID 1.

Eh? That isn't at all what the patch does...

Anyway, that patch only incidentally 'fixes' this, by changing the caller to use path_equals_ptr which null-checks; while a better commit is 105396778174a39bb04e9a78281ec7601e252d9f which fixes path_compare() itself (i.e. for all callers).

> Eh? That isn't at all what the patch does...

Before the patch, the `getenv("TERM")` call would not happen; now it does.

While fixing path_compare() may be a better long-term solution, I think the existing patch is appropriate for this bug/SRU.

Er, I see the problem in my description now. It's been a while since I looked at this patch. In any case, the patch is still appropriate.

This bug was fixed in the package systemd - 245.4-4ubuntu3.18

---------------
systemd (245.4-4ubuntu3.18) focal; urgency=medium

  [ Nick Rosbrook ]
  * core: make sure we don't get confused when setting TERM for a tty fd
    (LP: #1959475)
    File: debian/patches/lp1959475-core-make-sure-we-don-t-get-confused-when-setting-TERM-fo.patch
    https://git.launchpad.net/~ubuntu-core-dev/ubuntu/+source/systemd/commit/?id=b10c6853050dde26665caf3b15444d768d2bc498
  * shared/calendarspec: when mktime() moves us backwards, jump forward
    (LP: #1966800)
    File: debian/patches/lp1966800-shared-calendarspec-when-mktime-moves-us-backwards-jump-f.patch
    https://git.launchpad.net/~ubuntu-core-dev/ubuntu/+source/systemd/commit/?id=1f063541e44f6ff1a6904676d4264a2e49a09594
  * network: do not remove localhost address (LP: #1979951)
    File: debian/patches/lp1979951-network-do-not-remove-localhost-address.patch
    https://git.launchpad.net/~ubuntu-core-dev/ubuntu/+source/systemd/commit/?id=87f872b8c5451f353601fb606e7fd7a479217cef
  * units: remove the restart limit on the modprobe@.service (LP: #1982462)
    File: debian/patches/lp1982462-units-remove-the-restart-limit-on-the-modprobe-.service.patch
    https://git.launchpad.net/~ubuntu-core-dev/ubuntu/+source/systemd/commit/?id=68353ffaf3539e6a58ef62a8b50850f56eae29ea

  [ Mustafa Kemal Gilor ]
  * d/p/lp1978079-efi-pstore-not-cleared-on-boot.patch: pstore: Run after
    modules are loaded. Thanks to Alexander Graf <email address hidden>.
    (LP: #1978079)
    Author: Mustafa Kemal Gilor
    File: debian/patches/lp1978079-efi-pstore-not-cleared-on-boot.patch
    https://git.launchpad.net/~ubuntu-core-dev/ubuntu/+source/systemd/commit/?id=6e60756f2079d6408abdb967127a1d9b9a0eba8c

 -- Nick Rosbrook <email address hidden> Wed, 31 Aug 2022 11:27:33 -0400

The verification of the Stable Release Update for systemd has completed successfully and the package is now being released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.