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

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Date:	Wed, 10 Feb 2010 16:31:07 +1100
From:	Michael Neuling <mikey@...ling.org>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
cc:	Helge Deller <deller@....de>,
	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



In message <20100210141016.4D18.A69D9226@...fujitsu.com> you wrote:
> > 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/Li
nux
> > 
> > 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 sm
all stack for ls.
> "ulimit -s 27; ls "  wroks perfectly fine.

Arrh.  I asked Helge offline earlier to check what use to work on parisc
on 2.6.31.

I guess PPC has a nice clean non-bloated ABI :-D

Mikey
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