From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Subject: Re: [PATCH 11/11] protect architectures where THREAD_SIZE >=
 PAGE_SIZE against fork bombs
Date: Mon, 25 Jun 2012 11:38:18 -0700
Message-ID: <20120625183818.GH3869@google.com>
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To: Frederic Weisbecker <fweisbec-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Glauber Costa <glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Frederic Weisbecker <fweisbec-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, David Rientjes <rientjes-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Pekka Enberg <penberg-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Michal Hocko <mhocko-AlSwsSmVLrQ@public.gmane.org>, Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>, Christoph Lameter <cl-vYTEC60ixJUAvxtiuMwx3w@public.gmane.org>, devel-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org, kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org, Pekka Enberg <penberg-bbCR+/B0CizivPeTLB3BmA@public.gmane.org>, Suleiman Souhlal <suleiman-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>

On Mon, Jun 25, 2012 at 06:55:35PM +0200, Frederic Weisbecker wrote:
> On 06/25/2012 04:15 PM, Glauber Costa wrote:
> 
> > Because those architectures will draw their stacks directly from
> > the page allocator, rather than the slab cache, we can directly
> > pass __GFP_KMEMCG flag, and issue the corresponding free_pages.
> > 
> > This code path is taken when the architecture doesn't define
> > CONFIG_ARCH_THREAD_INFO_ALLOCATOR (only ia64 seems to), and has
> > THREAD_SIZE >= PAGE_SIZE. Luckily, most - if not all - of the
> > remaining architectures fall in this category.
> > 
> > This will guarantee that every stack page is accounted to the memcg
> > the process currently lives on, and will have the allocations to fail
> > if they go over limit.
> > 
> > For the time being, I am defining a new variant of THREADINFO_GFP, not
> > to mess with the other path. Once the slab is also tracked by memcg,
> > we can get rid of that flag.
> > 
> > Tested to successfully protect against :(){ :|:& };:
> > 
> > Signed-off-by: Glauber Costa <glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
> > CC: Christoph Lameter <cl-vYTEC60ixJUAvxtiuMwx3w@public.gmane.org>
> > CC: Pekka Enberg <penberg-bbCR+/B0CizivPeTLB3BmA@public.gmane.org>
> > CC: Michal Hocko <mhocko-AlSwsSmVLrQ@public.gmane.org>
> > CC: Kamezawa Hiroyuki <kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org>
> > CC: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
> > CC: Suleiman Souhlal <suleiman-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
> 
> 
> Acked-by: Frederic Weisbecker <fweisbec-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

Frederic, does this (with proper slab accounting added later) achieve
what you wanted with the task counter?

Thanks.

-- 
tejun