pppd exits with Fatal signal 11, on PAM auth.

[Joao Machado]

The crash occurs if the following PAM auth line is present when pppd tries to authenticate a user ("login" option)
auth optional pam_smbpass.so migrate

Apr 18 23:40:39 ubuntu pppd[1622]: Initializing PAM (3) for user j
Apr 18 23:40:39 ubuntu pppd[1622]: ---> PAM INIT Result = 0
Apr 18 23:40:39 ubuntu pppd[1622]: Attempting PAM authentication
Apr 18 23:40:39 ubuntu pppd[1622]: Fatal signal 11
Apr 18 23:40:39 ubuntu charon: 16[KNL] interface ppp0 deleted

This is seen at least on the following scenario:
1-L2TP vpn environment using xl2tpd + pppd
2-authentication method is PAP.
3-ppp version 2.4.5-5.1ubuntu2.2

The PAM config auth line is automatically added to "common-auth" when installing the following package
libpam-smbpass:i386 2:4.1.6+dfsg-1ubuntu2

# lsb_release -rd
Description: Ubuntu 14.04.4 LTS
Release: 14.04

[Launchpad Janitor (janitor)]

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