Date: Wed, 30 Mar 2005 21:40:34 +0200 (CEST)
From: Bodo Eggert <7eggert@gmx.de>
To: Wiktor <victorjan@poczta.onet.pl>
Cc: 7eggert@gmx.de, linux-kernel@vger.kernel.org
Subject: Re: [RFD] 'nice' attribute for executable files
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 <424ACEA9.6070401@poczta.onet.pl>
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On Wed, 30 Mar 2005, Wiktor wrote:

> my xmms problem is unimportant here, i've posted this thread to propose 
> some new feature in filesystem, not to solve problem with multimedia player!

You don't need a solution if there is no problem.

> max renice ulimit is quite good idea, but it allows to change nice of 
> *any* process user has permissions to.

In both of your examples (including the one below), the same thing 
applies.

> it could be implemented also, but 
>   the idea of 'nice' file attribute is to allow *only* some process be 
> run with lower nice. what's more, that nice would be *always* the same 
> (at process startup)!
> example:
> web server runs as user www. it spawns perl interpreter that root wants 
>   to be run with lower nice, but he doesn't want to allow 'www' user to 
>   renice *any* process (for eg. this user is shared with webmaster, and 
> webmaster is malicious person; i know, the webmaster could have another 
> accout, but maybe for some file-ownership reasons, root doesn't want to 
> create special account for him).

chown root.root /usr/local/cgi-bin/somescript
chmod 755 /usr/local/cgi-bin/somescript

---/etc/su1.priv---
alias somescript /usr/bin/nice -n -5 su wwwrun -- exec /usr/local/cgi-bin/somescript.pl

ask never
allow wwwrun prefix somescript
---

ln -s /usr/bin/su1 /srv/wwwroot/cgi-bin/somescript


If you need the same command for a group of users, you can use a wrapper 
scritp that will look at the $HOME variable (which is set from 
/etc/passwd)

> in this situation, setting nice-attribute for /usr/bin/perl solves the 
> problem.

perl -e'exec("/bin/sh");' would grant nice privileges to anybody, and 
that's not nice!

> remember, that this feature would also provide an easy way to 
> increase nice level.

Not for running processes.

> it can be done with shell script, but setting nice 
> value in file attributes is cleaner and easier to manage.

Obviously not.
-- 
Top 100 things you don't want the sysadmin to say:
35. Ummm... Didn't you say you turned it off?
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