linux-kernel - Re: x86: randomize brk() and RLIMIT

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Message-ID: <20071025171942.pjff7jbpempfcuri@m.safari.iki.fi>
Date:	Thu, 25 Oct 2007 20:19:42 +0300
From:	Sami Farin <safari-kernel@...ari.iki.fi>
To:	Linux kernel Mailing List <linux-kernel@...r.kernel.org>
Cc:	Jiri Kosina <jkosina@...e.cz>,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: x86: randomize brk() and RLIMIT_DATA

On Thu, Oct 25, 2007 at 16:46:26 +0200, Jiri Kosina wrote:
> On Thu, 25 Oct 2007, Arjan van de Ven wrote:
> 
> > > Would be neat if randomized brk and setrlimit(RLIMIT_DATA, ...)
> > > worked in a predictable way:
> > this isn't a valid case afaics; even on "traditional x86" (before we 
> > changed the address space layout, or even today if you have an unlimited 
> > stack rlimit) this isn't going to work. applications really shouldn't 
> > use (s)brk() but malloc(); you have to be able to fall back to mmap 
> > regardless of what you do.
> 
> I tend to agree here with Arjan. However it probably would make no harm to 
> make at least a little bit consisten behavior of setrlimit(), though it 
> has a little use in such cases.
> 
> Sami, does the patch below work for you?

Thanks, Jiri, now RLIMIT_DATA works as expected.

Using only RLIMIT_AS to limit processes' memory usage is not
very easy.  It includes also libraries mapped read-only,
I have to check/modify the limits when I update/add
libraries,...

Amazingly, I found a patch which seems to be just what I need:
http://marc.info/?l=linux-mm&m=118402827803338&w=4
Seems like that is not going to -mm or mainstream...

-- 
Do what you love because life is too short for anything else.

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