Possible bug in 5.1 - su / utmp

[Raymond Sundland]

I found this very interesting when I saw it originally, but then found 
it was probably a bug.

Basically, when I log into my 5.1-RELEASE box (compiled today from CVS), 
I can do a 'w' and get the following:

% w
10:39AM  up  5:01, 1 user, load averages: 0.00, 0.00, 0.00
USER             TTY      FROM              LOGIN@  IDLE WHAT
ray              p0       somehost         10:39AM     - w

Now, when I try to SU to root, this entry changes:

% su -
Password:
Last login: Tue Jun 24 07:44:19 on ttyp1
% whoami
root
% w
10:40AM  up  5:01, 1 user, load averages: 0.04, 0.01, 0.00
USER             TTY      FROM              LOGIN@  IDLE WHAT
root             p0       -                10:40AM     - w

So, it looks like the utmp entry is being made (again) for ttyp0 and 
recording it.  This would be fine from my perspective, but is misleading 
once I exit the root shell:

% exit
% whoami
ray
% w
10:42AM  up  5:03, 1 user, load averages: 0.01, 0.00, 0.00
USER             TTY      FROM              LOGIN@  IDLE WHAT
root             p0       -                10:40AM     - w


This may be a bug in PAM, since I don't think su calls login (or maybe 
it does?)  Note that this does not happen if I do not use the '-' option 
for su.  This also shows up in the lastlog:

root             ttyp2                     Tue Jun 24 10:40 - 10:43  (00:02)
ray              ttyp2    somehost         Tue Jun 24 10:39 - 10:40  (00:00)

Anyone have any information about this... know what the bug is?  Maybe 
it's a setting I have set that can be changed?

Thanks.