Comment 0 for bug 1067779

getlogin() call in new glibc checks /proc/self/loginuid presence and trust its value as most safe source (due it's audit-related nature). But default /etc/pam.d/common-account doesn't contains entry to pam_loginuid.so which modify /proc/self/loginuid properly. This breaks getlogin() at many scenarios like this:

(pam session without pam_loginuid)$ perl -e '$t=getlogin; print "$t\n";'
root
(pam session without pam_loginuid)$ id
uid=1000(...

lust because /proc/self/loginuid contains '0' value

If I add pam_loginuid.so to /etc/pam.d/common-account like http://manpages.ubuntu.com/manpages/precise/man8/pam_loginuid.8.html recommend, everything worked as expected:

(pam session with pam_loginuid)$ perl -e '$t=getlogin; print "$t\n";'
user
(pam session with pam_loginuid)$ id
uid=1000(...

# cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=12.04
DISTRIB_CODENAME=precise
DISTRIB_DESCRIPTION="Ubuntu 12.04 LTS"

# dpkg -l|fgrep libpam
ii libpam-ck-connector 0.4.5-2 ConsoleKit PAM module
ii libpam-modules 1.1.3-7ubuntu2 Pluggable Authentication Modules for PAM
ii libpam-modules-bin 1.1.3-7ubuntu2 Pluggable Authentication Modules for PAM - helper binaries
ii libpam-runtime 1.1.3-7ubuntu2 Runtime support for the PAM library
ii libpam0g 1.1.3-7ubuntu2 Pluggable Authentication Modules library