linux-kernel - Re: Fork Bombing Patch

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Date:	Mon, 20 Aug 2007 10:42:47 -0400
From:	Chris Snook <csnook@...hat.com>
To:	Anand Jahagirdar <anandjigar@...il.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: Fork Bombing Patch

Anand Jahagirdar wrote:
> Hi
>    As Per the Previous Discussion of my Patch,I think insted of using
> KERN_CRIT,it is better to lower the priority level to KERN_WARNING.
> thats why i used KERN_WARNING.it will warn administrator and its
> administrator responsibility to take whatever action he want to take.
> 
> anand

Philosophically, I'm okay with the idea of a forkbomb meriting KERN_WARN 
priority, but we should never have a printk that can be trivially triggered by 
an unprivileged user that gets anything higher than KERN_INFO.  If I'm an 
attacker, and I want to do bad things without getting logged, the first thing I 
do is launch a carefully-tuned forkbomb that doesn't bog down the system, just 
triggers this message as often as the ratelimit will allow.  Once /var/log is 
full, I can do my nastiness.  Administrators need to be able to protect against 
that kind of thing without losing the ability to log KERN_WARN and higher 
priority messages.

Also, I stand by my assertion that we should only be complaining if the hard 
limit is also exceeded, since it's totally valid for an application to 
self-constrain using soft limits.  It may be uncommon, but the people who happen 
to use whatever applications do this will be very unhappy when they update their 
kernel and /var fills up from this spew.

	-- Chris
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