byobu-config segfault with screen backend

[Nick B.]

[Impact]

 * Backport Debian fix for a crash in byobu due to libslang2

[Test Case]

 * byobu-screen
 * in there hit F9 or start byobu-config
 * without the fix this crashes

[Regression Potential]

 * This is changing a libs implementation and
    $ reverse-depends src:slang2 -r xenial
   is quite a long list. OTOH this is somewhat ok as the change is in
   Debian and Ubuntu for more than three releases now and nothing around
   it seems to have totally broken.
   Never the less the biggest risk I see is something unexpected in one of
   the other libslang2 users.

[Other Info]

 * n/a

---

When running byobu with the screen backend byobu-config segfaults when trying to open it by pressing F9.

Steps to reproduce.

1. Configure byobu to use screen for the backend
2. Press F9 to open the configuration menu
3. The console flashes then returns to your shell window.

Running byobu-config manually within a byobu screen session shows it's segfaulting. It does not crash running it outside of screen.

byobu:
  Installed: 5.101-0ubuntu1~wily
  Candidate: 5.101-0ubuntu1~wily
  Version table:
 *** 5.101-0ubuntu1~wily 0
        500 http://ppa.launchpad.net/byobu/ppa/ubuntu/ wily/main amd64 Packages
        100 /var/lib/dpkg/status
     5.97-0ubuntu1 0
        500 http://mirror.us.leaseweb.net/ubuntu/ wily/main amd64 Packages

[Launchpad Janitor (janitor)]

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

[Toshio Ito (debug-ito)]

I can confirm this bug.

My environment:

- Xubuntu 16.04 Xenial (beta1)
- byobu 5.102-0ubuntu1
- xfce4-terminal 0.6.3-2ubuntu1
- Japanese language environment (ja_JP.UTF-8)

[Launchpad Janitor (janitor)]

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

[Rob J (quantumparticleresearch)]

Affects me as well, 5.87-1.

[Corben (tobias-krummen)]

Experiencing the same issue on Ubuntu Server 16.04.2 LTS with byobu 5.106.
Within byobu (with screen backend) it segfaults:

kernel: [69271.057862] python3[8757]: segfault at 0 ip 00007faa6ca75982 sp 00007fff6e7f7c20 error 4 in libc-2.23.so[7faa6c9f2000+1bf000]

Outside via byobu-config it works.

[Stephen Hill (steve-d-hill)]

Have same problem on 16.04.4 with byobu package 5.106-0ubuntu1

[Stephen Hill (steve-d-hill)]

Found this reference to it - https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=837868

[Christian Ehrhardt  (paelzer)]

That would imply it was resolved in slang2 (libslang2) 2.3.0-4 which is in everything later than Xenial.

The change to consider for backporting would be https://git.launchpad.net/ubuntu/+source/slang2/tree/debian/patches/init-crash.patch?id=e633289c99ede705274a1b337a0deff5f8e08779

We should try to build a ppa to check if the referenced bug in comment #7 really would hold a fix to this byobu issue - setting server-next.

[Christian Ehrhardt  (paelzer)]

I have built a test ppa with the fix [1].

That fixes the issue for me, I'd need a review [2] to feel confident going forward but it LGTM.

[1]: https://launchpad.net/~ci-train-ppa-service/+archive/ubuntu/3309
[2]: https://code.launchpad.net/~paelzer/ubuntu/+source/slang2/+git/slang2/+merge/348667

[Christian Ehrhardt  (paelzer)]

I checked once more to be sure, artful (and later) is ok

[Christian Ehrhardt  (paelzer)]

Updated the Debian bug so they are aware as well.

[Christian Ehrhardt  (paelzer)]

MP was approved, sponsored into SRU queue ...

[Robie Basak (racb)]

Hello Nick, or anyone else affected,

Accepted slang2 into xenial-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/slang2/2.3.0-2ubuntu1.1 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 and change the tag from verification-needed-xenial to verification-done-xenial. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-xenial. In either case, details of your testing will help us make a better decision.

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

[Christian Ehrhardt  (paelzer)]

Xenial as-is - still crashing.

Updated to Proposed

# apt install libslang2
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following package was automatically installed and is no longer required:
  libfreetype6
Use 'apt autoremove' to remove it.
The following packages will be upgraded:
  libslang2
1 upgraded, 0 newly installed, 0 to remove and 21 not upgraded.
Need to get 415 kB of archives.
After this operation, 18.4 kB disk space will be freed.
Get:1 http://archive.ubuntu.com/ubuntu xenial-proposed/main amd64 libslang2 amd64 2.3.0-2ubuntu1.1 [415 kB]
Fetched 415 kB in 0s (2007 kB/s)
(Reading database ... 25655 files and directories currently installed.)
Preparing to unpack .../libslang2_2.3.0-2ubuntu1.1_amd64.deb ...
Unpacking libslang2:amd64 (2.3.0-2ubuntu1.1) over (2.3.0-2ubuntu1) ...
Processing triggers for libc-bin (2.23-0ubuntu10) ...
Setting up libslang2:amd64 (2.3.0-2ubuntu1.1) ...
Processing triggers for libc-bin (2.23-0ubuntu10) ...

Working without a crash now.
Setting verified.

[Launchpad Janitor (janitor)]

This bug was fixed in the package slang2 - 2.3.0-2ubuntu1.1

---------------
slang2 (2.3.0-2ubuntu1.1) xenial; urgency=medium

  * d/p/init-crash.patch: Fix crash on multiple initialisation when TERMCAP
    set (LP: #1537528)

 -- Christian Ehrhardt <email address hidden> Thu, 28 Jun 2018 11:06:04 +0200

[Łukasz Zemczak (sil2100)]

The verification of the Stable Release Update for slang2 has completed successfully and the package has now been 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.