linux-kernel - Re: Fork Bombing Attack

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Message-ID: <1865922a0705180619g2a997c2ch5d13be3e023630e0@mail.gmail.com>
Date:	Fri, 18 May 2007 16:19:56 +0300
From:	"Ahmed S. Darwish" <darwish.07@...il.com>
To:	"Anand Jahagirdar" <anandjigar@...il.com>
Cc:	"Valdis.Kletnieks@...edu" <Valdis.Kletnieks@...edu>,
	linux-kernel@...r.kernel.org
Subject: Re: Fork Bombing Attack

On 5/18/07, Anand Jahagirdar <anandjigar@...il.com> wrote:
> Hello All
>            I tried to execute a program which creates 8152 process.(
> i=0; while( i<14) i++ fork(); )  with ulimit 8200. This program
> created 8152 processes and then stopped and came back to command
> prompt. this proves that my machine do have sufficient resources to
> create 8000 processes.
>
>            I found one more interesting thing on the same machine
> having FC6 distribution and Linux Kernel 2.6.18. i have set "ulimit -u
> 100". after setting this limit i tried to execute fork bombing program
> with guest account. after executing it
>
> expected result:-  guest uesr should not able to fork another single
> process when it reaches to 100 processes count.
>
> actual result :-  kernel allow me to create another processes without
> giving error. due to this i tried to execute same fork bombing program
> on another terminal with guest account and this fork bombing attack
> killed the box completely and machine needed reboot.
>

I think if you want resource limiting per _UID_ (and not per _process_
as you did), you should use PAM module pam_limits.so. You can edit
those limits using the file /etc/security/limits.conf

Regards,
-- 
Ahmed S. Darwish
http://darwish-07.blogspot.com
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