[Bug 1628687] Re: Assertion failure when PID 1 receives a zero-length message over notify socket

[Martin Pitt]

> Martin, if you can point me at the xenial branch, we can push this
through the security pocket.

https://anonscm.debian.org/cgit/pkg-systemd/systemd.git/commit/?h=ubuntu-xenial&id=1aa1f84c
(this just cleans up the original -security update to still work with gbp pq)

https://anonscm.debian.org/cgit/pkg-systemd/systemd.git/commit/?h=ubuntu-xenial&id=a80398c79
https://anonscm.debian.org/cgit/pkg-systemd/systemd.git/commit/?h=ubuntu-xenial&id=0f6614488

I'm fine with landing this as part of the next SRU (I'll get it into
-proposed today). A local DoS (the original and this new one) isn't
particularly exciting after all. If you rather want to to handle this as
a security update, then you can grab these three patches, and I'll
rebase the branch/re-do the SRU again.

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https://bugs.launchpad.net/bugs/1628687

Title:
  Assertion failure when PID 1 receives a zero-length message over
  notify socket

Status in systemd:
  Fix Released
Status in systemd package in Ubuntu:
  Fix Released
Status in systemd source package in Xenial:
  In Progress
Status in systemd source package in Yakkety:
  Fix Released

Bug description:
  Environment:

  Xenial 16.04.1
  Amd64

  Description.

  Systemd fails an assertion in manager_invoke_notify_message when a
  zero-length message is received over /run/systemd/notify. This allows
  a local user to perform a denial-of-service attack against PID 1.

  How to trigger the bug:

  $ while true; do NOTIFY_SOCKET=/run/systemd/notify systemd-notify "";
  done

  The following entries are written into /var/log/syslog, at this point
  systemd is crashed.

  Sep 28 20:57:20 ubuntu systemd[1]: Started User Manager for UID 1000.
  Sep 28 20:57:28 ubuntu systemd[1]: Assertion 'n > 0' failed at ../src/core/manager.c:1501, function manager_invoke_notify_message(). Aborting.
  Sep 28 20:57:29 ubuntu systemd[1]: Caught <ABRT>, dumped core as pid 1307.
  Sep 28 20:57:29 ubuntu systemd[1]: Freezing execution.

  
  Public bug: https://github.com/systemd/systemd/issues/4234

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