The patch titled Subject: fork: protect architectures where THREAD_SIZE >= PAGE_SIZE against fork bombs has been added to the -mm tree. Its filename is fork-protect-architectures-where-thread_size-=-page_size-against-fork-bombs.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Glauber Costa <glommer@xxxxxxxxxxxxx> Subject: fork: protect architectures where THREAD_SIZE >= PAGE_SIZE against fork bombs 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@xxxxxxxxxxxxx> Acked-by: Frederic Weisbecker <fweisbec@xxxxxxxxxx> Acked-by: Kamezawa Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> Reviewed-by: Michal Hocko <mhocko@xxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Greg Thelen <gthelen@xxxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: JoonSoo Kim <js1304@xxxxxxxxx> Cc: Mel Gorman <mel@xxxxxxxxx> Cc: Pekka Enberg <penberg@xxxxxxxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxx> Cc: Suleiman Souhlal <suleiman@xxxxxxxxxx> Cc: Tejun Heo <tj@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/thread_info.h | 2 ++ kernel/fork.c | 4 ++-- 2 files changed, 4 insertions(+), 2 deletions(-) diff -puN include/linux/thread_info.h~fork-protect-architectures-where-thread_size-=-page_size-against-fork-bombs include/linux/thread_info.h --- a/include/linux/thread_info.h~fork-protect-architectures-where-thread_size-=-page_size-against-fork-bombs +++ a/include/linux/thread_info.h @@ -61,6 +61,8 @@ extern long do_no_restart_syscall(struct # define THREADINFO_GFP (GFP_KERNEL | __GFP_NOTRACK) #endif +#define THREADINFO_GFP_ACCOUNTED (THREADINFO_GFP | __GFP_KMEMCG) + /* * flag set/clear/test wrappers * - pass TIF_xxxx constants to these functions diff -puN kernel/fork.c~fork-protect-architectures-where-thread_size-=-page_size-against-fork-bombs kernel/fork.c --- a/kernel/fork.c~fork-protect-architectures-where-thread_size-=-page_size-against-fork-bombs +++ a/kernel/fork.c @@ -146,7 +146,7 @@ void __weak arch_release_thread_info(str static struct thread_info *alloc_thread_info_node(struct task_struct *tsk, int node) { - struct page *page = alloc_pages_node(node, THREADINFO_GFP, + struct page *page = alloc_pages_node(node, THREADINFO_GFP_ACCOUNTED, THREAD_SIZE_ORDER); return page ? page_address(page) : NULL; @@ -154,7 +154,7 @@ static struct thread_info *alloc_thread_ static inline void free_thread_info(struct thread_info *ti) { - free_pages((unsigned long)ti, THREAD_SIZE_ORDER); + free_memcg_kmem_pages((unsigned long)ti, THREAD_SIZE_ORDER); } # else static struct kmem_cache *thread_info_cache; _ Patches currently in -mm which might be from glommer@xxxxxxxxxxxxx are linux-next.patch memcg-make-it-possible-to-use-the-stock-for-more-than-one-page.patch memcg-reclaim-when-more-than-one-page-needed.patch memcg-change-defines-to-an-enum.patch memcg-kmem-accounting-basic-infrastructure.patch mm-add-a-__gfp_kmemcg-flag.patch memcg-kmem-controller-infrastructure.patch mm-allocate-kernel-pages-to-the-right-memcg.patch res_counter-return-amount-of-charges-after-res_counter_uncharge.patch memcg-kmem-accounting-lifecycle-management.patch memcg-use-static-branches-when-code-not-in-use.patch memcg-allow-a-memcg-with-kmem-charges-to-be-destructed.patch memcg-execute-the-whole-memcg-freeing-in-free_worker.patch fork-protect-architectures-where-thread_size-=-page_size-against-fork-bombs.patch memcg-add-documentation-about-the-kmem-controller.patch slab-slub-struct-memcg_params.patch slab-annotate-on-slab-caches-nodelist-locks.patch slab-slub-consider-a-memcg-parameter-in-kmem_create_cache.patch memcg-allocate-memory-for-memcg-caches-whenever-a-new-memcg-appears.patch memcg-infrastructure-to-match-an-allocation-to-the-right-cache.patch memcg-skip-memcg-kmem-allocations-in-specified-code-regions.patch slb-always-get-the-cache-from-its-page-in-kmem_cache_free.patch slb-allocate-objects-from-memcg-cache.patch memcg-destroy-memcg-caches.patch memcg-slb-track-all-the-memcg-children-of-a-kmem_cache.patch memcg-slb-shrink-dead-caches.patch memcg-aggregate-memcg-cache-values-in-slabinfo.patch slab-propagate-tunable-values.patch slub-slub-specific-propagation-changes.patch kmem-add-slab-specific-documentation-about-the-kmem-controller.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html