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

[Frederic Weisbecker]

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>


Thanks!