From patchwork Mon May 23 22:17:36 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Emese Revfy X-Patchwork-Id: 9132465 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 307AD607D5 for ; Mon, 23 May 2016 22:10:49 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 25D8828164 for ; Mon, 23 May 2016 22:10:49 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 1A9712824D; Mon, 23 May 2016 22:10:49 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.1 required=2.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED, FREEMAIL_FROM, RCVD_IN_DNSWL_MED, T_DKIM_INVALID autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id 4791728164 for ; Mon, 23 May 2016 22:10:48 +0000 (UTC) Received: (qmail 11781 invoked by uid 550); 23 May 2016 22:10:46 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Reply-To: kernel-hardening@lists.openwall.com Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 11751 invoked from network); 23 May 2016 22:10:45 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=date:from:to:cc:subject:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=FjViA9k+KaopZRYOVsPQJVWvJ9MlaMRGRGPs0HXYzgc=; b=gbrBrHXHF3kDYVmuoLrh2JqvxCKFRsJ55A3QjOFNqMtl4+UyZOUtRovnlYNtgMDwIV /ecQE98C3Ff/uxkWlGt/F6U1korfq6ngQmlIzWQ7bKHq0jZiRu/pOHEi1wrRsvO4bzeL FkA+ZROjoTsw156hlTofMS6drvUnB9ocDwXG12dJPSA2L/bS9dPrn0n05wc/TqXsXXXb aRRgGcU+SQ+IlSex06OW7s/1FOl7+IXlyXf11GUU02lKysFieP4SNIUKdzjeSTa8kszw Chvt3GjyWYoGIRBfduPB489q1WzeHq8l80JnloejLL1GS7hyMKHiJcX6Y/ReGNcOr5kp c2lw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to:cc:subject:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=FjViA9k+KaopZRYOVsPQJVWvJ9MlaMRGRGPs0HXYzgc=; b=GS5l5gsWUhjPQPQXUhgUZPR+m6dQfF722leIa3QLHt6jNlJYQBhomSCT2UaTYS/fVJ HJVywVbE872cIACAxUdLRFoE2lsdu5QdnwDQkqDdQpIR/ISPRFL4gAcPMNL4FN8ue+7i jqgXcto7C8ZzK+ypby/iQOJ0z5hjczg26B2m8uXwhn2WxwcGOTZrGADvMBtAlEGgd296 xjsuAQW0Q4DvOSJbJZF2IEFFCuKKW7fj4e530SzsZeQWoNRr1JUiDhZoQoYodVAivrTR P9qawL8QjYMchlg1eoUKjhUzIj2XevMT9T+VIGQf/CZIcvM3UJcZPYlkChTma9DAacJk p+DA== X-Gm-Message-State: AOPr4FWhUIs311o6IzsqZ9tQoZKa7AVHny48Y8Ptc+KEoJ6/8+7JE12s2l0EFHRa5R7N0w== X-Received: by 10.28.145.73 with SMTP id t70mr18621445wmd.97.1464041434290; Mon, 23 May 2016 15:10:34 -0700 (PDT) Date: Tue, 24 May 2016 00:17:36 +0200 From: Emese Revfy To: kernel-hardening@lists.openwall.com Cc: pageexec@freemail.hu, spender@grsecurity.net, mmarek@suse.com, keescook@chromium.org, linux-kernel@vger.kernel.org, yamada.masahiro@socionext.com, linux-kbuild@vger.kernel.org, tytso@mit.edu, akpm@linux-foundation.org, linux-mm@kvack.org, axboe@kernel.dk, viro@zeniv.linux.org.uk, paulmck@linux.vnet.ibm.com, mingo@redhat.com, tglx@linutronix.de, bart.vanassche@sandisk.com, davem@davemloft.net Message-Id: <20160524001736.135ae3cdc101ecec3232a493@gmail.com> In-Reply-To: <20160524001405.3e6abd1d5a63a871cc366cff@gmail.com> References: <20160524001405.3e6abd1d5a63a871cc366cff@gmail.com> X-Mailer: Sylpheed 3.5.0 (GTK+ 2.24.30; x86_64-pc-linux-gnu) Mime-Version: 1.0 Subject: [kernel-hardening] [PATCH v1 3/3] Add the extra_latent_entropy kernel parameter X-Virus-Scanned: ClamAV using ClamSMTP When extra_latent_entropy is passed on the kernel command line, entropy will be extracted from up to the first 4GB of RAM while the runtime memory allocator is being initialized. Based on work created by the PaX Team. Signed-off-by: Emese Revfy --- Documentation/kernel-parameters.txt | 5 +++++ arch/Kconfig | 5 +++++ mm/page_alloc.c | 23 +++++++++++++++++++++++ 3 files changed, 33 insertions(+) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 5349363..6c2496e 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -2862,6 +2862,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted. the specified number of seconds. This is to be used if your oopses keep scrolling off the screen. + extra_latent_entropy + Enable a very simple form of latent entropy extraction + from the first 4GB of memory as the bootmem allocator + passes the memory pages to the buddy allocator. + pcbit= [HW,ISDN] pcd. [PARIDE] diff --git a/arch/Kconfig b/arch/Kconfig index 74489df..327d1e4 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -403,6 +403,11 @@ config GCC_PLUGIN_LATENT_ENTROPY there is little 'natural' source of entropy normally. The cost is some slowdown of the boot process and fork and irq processing. + When extra_latent_entropy is passed on the kernel command line, + entropy will be extracted from up to the first 4GB of RAM while the + runtime memory allocator is being initialized. This costs even more + slowdown of the boot process. + Note that entropy extracted this way is not known to be cryptographically secure! diff --git a/mm/page_alloc.c b/mm/page_alloc.c index ffc4f4a..c79407b 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -63,6 +63,7 @@ #include #include #include +#include #include #include @@ -1235,6 +1236,15 @@ static void __free_pages_ok(struct page *page, unsigned int order) } #ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY +bool __meminitdata extra_latent_entropy; + +static int __init setup_extra_latent_entropy(char *str) +{ + extra_latent_entropy = true; + return 0; +} +early_param("extra_latent_entropy", setup_extra_latent_entropy); + volatile u64 latent_entropy __latent_entropy; EXPORT_SYMBOL(latent_entropy); #endif @@ -1254,6 +1264,19 @@ static void __init __free_pages_boot_core(struct page *page, unsigned int order) __ClearPageReserved(p); set_page_count(p, 0); +#ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY + if (extra_latent_entropy && !PageHighMem(page) && page_to_pfn(page) < 0x100000) { + u64 hash = 0; + size_t index, end = PAGE_SIZE * nr_pages / sizeof hash; + const u64 *data = lowmem_page_address(page); + + for (index = 0; index < end; index++) + hash ^= hash + data[index]; + latent_entropy ^= hash; + add_device_randomness((const void *)&latent_entropy, sizeof(latent_entropy)); + } +#endif + page_zone(page)->managed_pages += nr_pages; set_page_refcounted(page); __free_pages(page, order);