linux-kernel - Re: Fork Bombing Patch

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Date:	Thu, 23 Aug 2007 13:52:20 +0200
From:	Krzysztof Halasa <khc@...waw.pl>
To:	"Anand Jahagirdar" <anandjigar@...il.com>
Cc:	"Chris Snook" <csnook@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: Fork Bombing Patch

Hi,

"Anand Jahagirdar" <anandjigar@...il.com> writes:

>    I am forwarding one more improved patch which i have modified as
> per your suggestions. Insted of KERN_INFO i have used KERN_NOTICE and
> i have added one more if block to check hard limit. how good it is?

Not very, still lacks "#ifdef CONFIG_something" and the required
Kconfig change (or other runtime thing defaulting to "no printk").

And now, it seems, the "goto bad_fork_tree" (not only printk())
ignores the soft limit -> really bad.

> +++ root/Desktop/a1/linux-2.6.17.tar.bz2_FILES/linux-2.6.17/kernel/fork.c	2007-06-26 20:41:41.000000000 +0530
> @@ -957,12 +957,19 @@
>  
>  	retval = -EAGAIN;
>  	
> -        
> +        /*
> +         * following code does not allow Non Root User to cross its process
> +         * limit and it alerts administrator about user Nearing the process limit.
> +         */
> + 
>        	if (atomic_read(&p->user->processes) >= p->signal->rlim[RLIMIT_NPROC].rlim_cur) 
> +		 if (atomic_read(&p->user->processes) >= p->signal->rlim[RLIMIT_NPROC].rlim_max)
> 	 		if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
> -				p->user != &root_user) 
> +				p->user != &root_user)  {
> +                        	if (printk_ratelimit())
> +                               	 printk(KERN_NOTICE "User with uid %u is Nearing the process limit\n",p->user->uid);
> +
>  			 	goto bad_fork_free;
> -			
> +			}			
>  			
>  	atomic_inc(&p->user->__count);
>  	atomic_inc(&p->user->processes);

-- 
Krzysztof Halasa
-
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