Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758192Ab2HINEE (ORCPT ); Thu, 9 Aug 2012 09:04:04 -0400 Received: from mailhub.sw.ru ([195.214.232.25]:13179 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751699Ab2HINCw (ORCPT ); Thu, 9 Aug 2012 09:02:52 -0400 From: Glauber Costa To: Cc: , , , Michal Hocko , Johannes Weiner , Andrew Morton , , Christoph Lameter , David Rientjes , Pekka Enberg , Glauber Costa , Pekka Enberg , Suleiman Souhlal Subject: [PATCH v2 11/11] protect architectures where THREAD_SIZE >= PAGE_SIZE against fork bombs Date: Thu, 9 Aug 2012 17:01:19 +0400 Message-Id: <1344517279-30646-12-git-send-email-glommer@parallels.com> X-Mailer: git-send-email 1.7.11.2 In-Reply-To: <1344517279-30646-1-git-send-email-glommer@parallels.com> References: <1344517279-30646-1-git-send-email-glommer@parallels.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2895 Lines: 75 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 Acked-by: Frederic Weisbecker CC: Christoph Lameter CC: Pekka Enberg CC: Michal Hocko CC: Kamezawa Hiroyuki CC: Johannes Weiner CC: Suleiman Souhlal --- include/linux/thread_info.h | 2 ++ kernel/fork.c | 4 ++-- 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h index ccc1899..e7e0473 100644 --- a/include/linux/thread_info.h +++ b/include/linux/thread_info.h @@ -61,6 +61,8 @@ extern long do_no_restart_syscall(struct restart_block *parm); # 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 --git a/kernel/fork.c b/kernel/fork.c index dc3ff16..b0b90c3 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -142,7 +142,7 @@ void __weak arch_release_thread_info(struct thread_info *ti) { } 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; @@ -151,7 +151,7 @@ static struct thread_info *alloc_thread_info_node(struct task_struct *tsk, static inline void free_thread_info(struct thread_info *ti) { arch_release_thread_info(ti); - free_pages((unsigned long)ti, THREAD_SIZE_ORDER); + free_accounted_pages((unsigned long)ti, THREAD_SIZE_ORDER); } # else static struct kmem_cache *thread_info_cache; -- 1.7.11.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/