Surprise : /proc/keys file depends on who is looking, super user can not see data of other users

[Lev Olshvang]

I have just noticed that   result of the cat /proc/keys command
displays different output for root and regular user, and the output for 
the root
user does not include keys of other users

(I see implementation for this in kernel tree  security/keys/proc.c - 
proc_key_users_show()


Is it some kind of security policy in Linux ? because I used to think 
that as a superuser I have access for all
information.
(kernel 2.6.36.2)