From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f178.google.com (mail-wi0-f178.google.com [209.85.212.178]) by kanga.kvack.org (Postfix) with ESMTP id AC2396B006C for ; Fri, 24 Apr 2015 17:06:19 -0400 (EDT) Received: by wiun10 with SMTP id n10so33100912wiu.1 for ; Fri, 24 Apr 2015 14:06:19 -0700 (PDT) Received: from mail-wi0-f174.google.com (mail-wi0-f174.google.com. [209.85.212.174]) by mx.google.com with ESMTPS id q8si813167wif.7.2015.04.24.14.06.18 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 24 Apr 2015 14:06:18 -0700 (PDT) Received: by widdi4 with SMTP id di4so33141837wid.0 for ; Fri, 24 Apr 2015 14:06:18 -0700 (PDT) From: Anisse Astier Subject: [PATCH 2/2] mm/page_alloc.c: add config option to sanitize freed pages Date: Fri, 24 Apr 2015 23:05:49 +0200 Message-Id: <1429909549-11726-3-git-send-email-anisse@astier.eu> In-Reply-To: <1429909549-11726-1-git-send-email-anisse@astier.eu> References: <1429909549-11726-1-git-send-email-anisse@astier.eu> Sender: owner-linux-mm@kvack.org List-ID: Cc: Anisse Astier , Andrew Morton , Mel Gorman , "Kirill A. Shutemov" , David Rientjes , Alan Cox , Linus Torvalds , Peter Zijlstra , PaX Team , Brad Spengler , Kees Cook , linux-mm@kvack.org, linux-kernel@vger.kernel.org This new config option will sanitize all freed pages. This is a pretty low-level change useful to track some cases of use-after-free, help kernel same-page merging in VM environments, and counter a few info leaks. Signed-off-by: Anisse Astier --- mm/Kconfig | 12 ++++++++++++ mm/page_alloc.c | 5 +++++ 2 files changed, 17 insertions(+) diff --git a/mm/Kconfig b/mm/Kconfig index 390214d..cb2df5f 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -635,3 +635,15 @@ config MAX_STACK_SIZE_MB changed to a smaller value in which case that is used. A sane initial value is 80 MB. + +config SANITIZE_FREED_PAGES + bool "Sanitize memory pages after free" + default n + help + This option is used to make sure all pages freed are zeroed. This is + quite low-level and doesn't handle your slab buffers. + It has various applications, from preventing some info leaks to + helping kernel same-page merging in virtualised environments. + Depending on your workload, it will reduce performance of about 3%. + + If unsure, say N. diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 05fcec9..c71440a 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -803,6 +803,11 @@ static bool free_pages_prepare(struct page *page, unsigned int order) debug_check_no_obj_freed(page_address(page), PAGE_SIZE << order); } + +#ifdef CONFIG_SANITIZE_FREED_PAGES + zero_pages(page, order); +#endif + arch_free_page(page, order); kernel_map_pages(page, 1 << order, 0); -- 1.9.3 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org