From patchwork Wed May 24 15:57:47 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Rik van Riel X-Patchwork-Id: 9746361 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 142076032B for ; Wed, 24 May 2017 16:12:49 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 026BD28985 for ; Wed, 24 May 2017 16:12:49 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id E9259289BB; Wed, 24 May 2017 16:12:48 +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=-1.9 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [65.50.211.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 7186A28985 for ; Wed, 24 May 2017 16:12:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:MIME-Version:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:References: In-Reply-To:Message-Id:Date:Subject:To:From:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=3lmJezxoe6TMLyct80Fv5OKRfldY16DlN/kS7vxBC4g=; b=gjpHy23IBbwH6J1HE2OXbiP4oF /WFs+QVJjoIEzTU8IiGCApqAQ6EDIZjowMm8n6OWH+kQRwB/fZNEbdTRPm++hnkrE1AvDjTe26x8v mkj/ftjIkSRPgnx9wVlqhH7yBKcu1zlqwUSLREAgOPoRcQNqDxw5cbAWp2r6qZBNimfAIEgPiOnaj rj7BX27DOzCyl0B/WMKb+dgO7ryTXbNpuz4EgIq02OEZoTEdntvO+Mq85xnhvF++nUZ9H1+dXNTUD LxuH9pZAx3Yv3H/0LQT2n7T9cu3RyFpyYewWX4yYxGQ1RX6oCifLWroIXytuVNED8GH98MYpbi8qP ThMtEK8w==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.87 #1 (Red Hat Linux)) id 1dDYty-00061f-Qm; Wed, 24 May 2017 16:12:46 +0000 Received: from shelob.surriel.com ([96.67.55.147]) by bombadil.infradead.org with esmtps (Exim 4.87 #1 (Red Hat Linux)) id 1dDYg5-0006NK-7h for linux-arm-kernel@lists.infradead.org; Wed, 24 May 2017 15:58:28 +0000 Received: from [2001:470:1f07:12aa:224:e8ff:fe38:995c] (helo=annuminas.surriel.com) by shelob.surriel.com with esmtps (TLSv1:AES256-SHA:256) (Exim 4.63) (envelope-from ) id 1dDYfd-0004jv-1H; Wed, 24 May 2017 11:57:57 -0400 Received: from annuminas.surriel.com (localhost.localdomain [127.0.0.1]) by annuminas.surriel.com (8.15.2/8.14.5) with ESMTP id v4OFvut8000732; Wed, 24 May 2017 11:57:56 -0400 Received: (from riel@localhost) by annuminas.surriel.com (8.15.2/8.15.2/Submit) id v4OFvunu000731; Wed, 24 May 2017 11:57:56 -0400 X-Authentication-Warning: annuminas.surriel.com: riel set sender to riel@redhat.com using -f From: riel@redhat.com To: linux-kernel@vger.kernel.org Subject: [PATCH 1/5] random, stackprotect: introduce get_random_canary function Date: Wed, 24 May 2017 11:57:47 -0400 Message-Id: <20170524155751.424-2-riel@redhat.com> X-Mailer: git-send-email 2.9.3 In-Reply-To: <20170524155751.424-1-riel@redhat.com> References: <20170524155751.424-1-riel@redhat.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20170524_085825_414139_A6D62BD4 X-CRM114-Status: UNSURE ( 9.08 ) X-CRM114-Notice: Please train this message. X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: tytso@mit.edu, keescook@chromium.org, ysato@users.sourceforge.jp, linux-sh@vger.kernel.org, catalin.marinas@arm.com, x86@kernel.org, luto@amacapital.net, danielmicay@gmail.com, hpa@zytor.com, kernel-hardening@lists.openwall.com, mingo@kernel.org, linux-arm-kernel@lists.infradead.org MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP From: Rik van Riel Introduce the get_random_canary function, which provides a random unsigned long canary value with the first byte zeroed out on 64 bit architectures, in order to mitigate non-terminated C string overflows. The null byte both prevents C string functions from reading the canary, and from writing it if the canary value were guessed or obtained through some other means. Reducing the entropy by 8 bits is acceptable on 64-bit systems, which will still have 56 bits of entropy left, but not on 32 bit systems, so the "ascii armor" canary is only implemented on 64-bit systems. Inspired by the "ascii armor" code in the old execshield patches, and Daniel Micay's linux-hardened tree. Signed-off-by: Rik van Riel Acked-by: Kees Cook --- include/linux/random.h | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/include/linux/random.h b/include/linux/random.h index ed5c3838780d..1fa0dc880bd7 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -57,6 +57,27 @@ static inline unsigned long get_random_long(void) #endif } +/* + * On 64-bit architectures, protect against non-terminated C string overflows + * by zeroing out the first byte of the canary; this leaves 56 bits of entropy. + */ +#ifdef CONFIG_64BIT +# ifdef __LITTLE_ENDIAN +# define CANARY_MASK 0xffffffffffffff00UL +# else /* big endian, 64 bits: */ +# define CANARY_MASK 0x00ffffffffffffffUL +# endif +#else /* 32 bits: */ +# define CANARY_MASK 0xffffffffUL +#endif + +static inline unsigned long get_random_canary(void) +{ + unsigned long val = get_random_long(); + + return val & CANARY_MASK; +} + unsigned long randomize_page(unsigned long start, unsigned long range); u32 prandom_u32(void);