[Bug 1723956] Re: busybox-static: several network applets segfaulting

[Steve Langasek]

Thanks, adding a systemd task to this bug for libnss-resolve.

It may be that this bug is only reproducible in 17.04 because that was
the only release in which libnss-resolve was installed by default.  (We
dropped this package from ubuntu-standard in 17.10.)

This also may not be fixable on the systemd side, since the failure
happens with a static binary calling into an NSS module that calls into
pthreads.

And it may not be fixable in busybox without substantial rework of the
'nslookup' applet, which appears to only front onto the glibc resolver
apis instead of actually talking to the specified nameserver... which is
what nslookup is defined to do.

** Changed in: busybox (Ubuntu)
       Status: Incomplete => Triaged

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https://bugs.launchpad.net/bugs/1723956

Title:
  busybox-static: several network applets segfaulting

Status in busybox package in Ubuntu:
  Triaged
Status in systemd package in Ubuntu:
  New

Bug description:
  On a fully up-to-date Ubuntu 17.04, running most applets from busybox-
  static that are network-related lead to a segfault. Example:

  $ busybox nslookup google.com 8.8.8.8
  Server:    8.8.8.8
  Segmentation fault

  $ busybox        
  BusyBox v1.22.1 (Ubuntu 1:1.22.0-19ubuntu2) multi-call binary.
  [...]

  $ apt-cache policy busybox
  busybox:
    Installed: (none)
    Candidate: 1:1.22.0-19ubuntu2
    Version table:
       1:1.22.0-19ubuntu2 500
          500 http://ftp.fau.de/ubuntu zesty/universe amd64 Packages

  $ dpkg -S /bin/busybox 
  busybox-static: /bin/busybox

  $ apt-cache policy busybox-static
  busybox-static:
    Installed: 1:1.22.0-19ubuntu2
    Candidate: 1:1.22.0-19ubuntu2
    Version table:
   *** 1:1.22.0-19ubuntu2 500
          500 http://ftp.fau.de/ubuntu zesty/main amd64 Packages
          100 /var/lib/dpkg/status


  This even happens when passing invalid domains or DNS servers to use
  that don't actually run any DNS service. (like "busybox nslookup
  google.com 1.2.3.4" or "busybox nslookup bar.foof00 8.8.8.8"), so it
  seems to be early in the network setup.

  I could not reproduce the problem on the very same system when compiling stock busybox 1.22.1 (why even? we're at 1.27.x!) myself, neither with a recent git clone. Also two VMs I had at hand running Ubuntu 14.04 and 16.04 didn't show this problem with busybox-static. Installing the package "busybox" (which removes busybox-static) fixes the problem on 17.04.
  The only thing that might be related in any way about my system is that it has no IPv6 connectivity (apart from the link-local address).

  I also sent a crash report when the apport window popped up, but I
  have no idea where this ends up and how to add further information,
  hence this report here. Please let me know if this seemingly trivial
  bug cannot be reproduced instantly, so I can try to assist with
  further information.

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