linux-kernel - Re: [PATCH 2/4] posix-timers: limit the number of posix timers per process

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Date:	Fri, 2 Sep 2011 11:30:47 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Andi Kleen <andi@...stfloor.org>
cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	eric.dumazet@...il.com, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 2/4] posix-timers: limit the number of posix timers per
 process

On Mon, 29 Aug 2011, Andi Kleen wrote:

> From: Andi Kleen <ak@...ux.intel.com>
> 
> Now this is the main reason I wrote the whole patchkit: previously
> there was no limit on the maximum number of POSIX timers a process
> could allocate.  This limits the amount of unswappable kernel memory
> a process can pin down this way.
> 
> With the POSIX timer ids being per process we can do this limit
> per process now without allowing one process DoSing another.
> 
> I implemented it as a sysctl, not a rlimit for now, because
> there was no clear use case for rlimit.

rlimit please.

>  /*
>   * we assume that the new SIGEV_THREAD_ID shares no bits with the other
>   * SIGEV values.  Here we put out an error if this assumption fails.
> @@ -572,6 +574,12 @@ SYSCALL_DEFINE3(timer_create, const clockid_t, which_clock,
>  
>  	it_id_set = IT_ID_SET;
>  	new_timer->it_id = (timer_t) new_timer_id;
> +
> +	if (new_timer_id >= sysctl_max_posix_timers) {
> +		error = -EMFILE;  /* better error? */

EPERM might work as well

Thanks,

	tglx
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