[Bug 1696499] Re: dhclient segfaults on ubuntu 17.04

[Edward Jiang]

Inspection of the core dump and some testing proves the Segmentation
fault error is caused by denied permission to read /proc/self/cmdline.
Moving the executable anywhere else the problem would simply disappear.

Further inspection pointed the cause to be apparmor denied the open file
call, thus, the obvious workaround is remove /sbin/dhclient's apparmor
from enforcing mode:

sudo apt install apparmor-utils
sudo aa-complain /sbin/dhclient

This would allow the dhclient to run without error.

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https://bugs.launchpad.net/bugs/1696499

Title:
  dhclient segfaults on ubuntu 17.04

Status in isc-dhcp package in Ubuntu:
  Confirmed

Bug description:
  After upgrading, network-manager stopped running DHCP, after trying to
  run dhclient myself I found out it segfaults. Attached is its strace
  output.

  I can connect to the internet by stopping network-manager and using
  ifconfig + route + /etc/resolv.conf.

  Output:
  guy at golem4:~$ dhclient
  Segmentation fault (core dumped)

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