Reset of limits with su / new session

[Reuti <reuti@staff.uni-marburg.de>]

Hi all,

while wondering about missing ulimits for an interactive session  
scheduled by SGE (SUN GridEngine) to a node in a cluster running on  
Debian (which is working fine with other Linux distributions), I also  
found, that each user can increase his limits again by a simple su to  
his own account:

$ ulimit -t 55
$ ulimit -aH
...
cpu time             (seconds, -t) 55
...
$ su - reuti
Password:
$ ulimit -aH
...
cpu time             (seconds, -t) unlimited
...

Digging around I finally found this:

--- pam-0.76.orig/debian/patches-applied/
027_pam_limits_better_init_allow_explicit_root
+++ pam-0.76/debian/patches-applied/
027_pam_limits_better_init_allow_explicit_root
@@ -0,0 +1,100 @@
+Allow explicit limits for root.
+Also, remove limits on su.
+Index: Linux-PAM/modules/pam_limits/pam_limits.c

Seems, that I can get the desired behavior by changing this back. But  
more interesting is the question: why was this patch applied to  
pam_ulimits.c in Debian? What is the advantage of allowing a user to  
circumvent any imposed limits?

Cheers - Reuti