[Devel] Re: [PATCH 11/11] protect architectures where THREAD_SIZE >= PAGE_SIZE against fork bombs

[Tejun Heo]

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 at parallels.com>
> > CC: Christoph Lameter <cl at linux.com>
> > CC: Pekka Enberg <penberg at cs.helsinki.fi>
> > CC: Michal Hocko <mhocko at suse.cz>
> > CC: Kamezawa Hiroyuki <kamezawa.hiroyu at jp.fujitsu.com>
> > CC: Johannes Weiner <hannes at cmpxchg.org>
> > CC: Suleiman Souhlal <suleiman at google.com>
> 
> 
> Acked-by: Frederic Weisbecker <fweisbec at redhat.com>

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

Thanks.

-- 
tejun