linux-kernel - Re: [PATCH] Restrict initial stack space expansion to rlimit

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Message-Id: <20100210141016.4D18.A69D9226@jp.fujitsu.com>
Date:	Wed, 10 Feb 2010 14:12:51 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Helge Deller <deller@....de>
Cc:	kosaki.motohiro@...fujitsu.com,
	Michael Neuling <mikey@...ling.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Americo Wang <xiyou.wangcong@...il.com>,
	Anton Blanchard <anton@...ba.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Oleg Nesterov <oleg@...hat.com>,
	James Morris <jmorris@...ei.org>, Ingo Molnar <mingo@...e.hu>,
	linux-fsdevel@...r.kernel.org, stable@...nel.org,
	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org,
	Serge Hallyn <serue@...ibm.com>,
	Paul Mackerras <paulus@...ba.org>, benh@...nel.crashing.org,
	miltonm@....com, aeb@....nl, linux-parisc@...r.kernel.org
Subject: Re: [PATCH] Restrict initial stack space expansion to rlimit

> On 02/09/2010 10:51 PM, Michael Neuling wrote:
> >>> I'd still like someone with a CONFIG_STACK_GROWSUP arch to test/ACK it
> >>> as well.
> >>
> >> There's only one CONFIG_GROWSUP arch - parisc.
> >> Could someone please test it on parisc?
> 
> I did.
> 
> > How about doing:
> >    'ulimit -s 15; ls'
> > before and after the patch is applied.  Before it's applied, 'ls' should
> > be killed.  After the patch is applied, 'ls' should no longer be killed.
> >
> > I'm suggesting a stack limit of 15KB since it's small enough to trigger
> > 20*PAGE_SIZE.  Also 15KB not a multiple of PAGE_SIZE, which is a trickier
> > case to handle correctly with this code.
> >
> > 4K pages on parisc should be fine to test with.
> 
> Mikey, thanks for the suggested test plan.
> 
> I'm not sure if your patch does it correct for parisc/stack-grows-up-case.
> 
> I tested your patch on  a 4k pages kernel:
> root@...00:~# uname -a
> Linux c3000 2.6.33-rc7-32bit #221 Tue Feb 9 23:17:06 CET 2010 parisc GNU/Linux
> 
> Without your patch:
> root@...00:~# ulimit -s 15; ls
> Killed
> -> correct.
> 
> With your patch:
> root@...00:~# ulimit -s 15; ls
> Killed
> _or_:
> root@...00:~# ulimit -s 15; ls
> Segmentation fault
> -> ??
> 
> Any idea?

My x86_64 box also makes segmentation fault. I think "ulimit -s 15" is too small stack for ls.
"ulimit -s 27; ls "  wroks perfectly fine.



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