Comment 1 for bug 1094990

Using Mint14/Cinnamon 64. I have a very similar issue which I think is the same bug. I think PAM is not setting the umask at all when logging in via mdm.

/etc/login.defs contains the following:
UMASK 027
USERGROUPS_ENAB yes

and users are in their own private groups.

Logging in via mdm and in a terminal emulator the umask is set to some unconfigured value (it is not set in either /etc/profile or ~/.profile). If I log in via the command line (either via su or using CTRL-ALT-F1 etc) then pam_umask works as expected:

matt@matt-X201 ~ $ umask
0022
matt@matt-X201 ~ $ su matt
Password:
matt@matt-X201 ~ $ umask
0007

As a test I have also tried explicitly setting the umask in /etc/pam.d/common-session by modifying the pam_umask.so line:
session optional pam_umask.so umask=001

This gives the same behaviour:
matt@matt-X201 ~ $ umask
0022
matt@matt-X201 ~ $ su matt
Password:
matt@matt-X201 ~ $ umask
0001

I have checked the mdm pam configuration and it sources common-session:
matt@matt-X201 ~ $ grep common-session /etc/pam.d/mdm
@include common-session

This suggests to me that the problem is with mdm.