From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 919D4C43331 for ; Wed, 25 Mar 2020 13:21:38 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 67012207FF for ; Wed, 25 Mar 2020 13:21:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="UrrbKD3K" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 67012207FF Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=RbBzxm0U3CZ82JTw3R18xHPEzbTzllnAiEOykT40Lyg=; b=UrrbKD3Kc3apLC 8+m6CTkMvo1ZA2v3ueJQ057QXj9kQAfSVn/ARJ00ctJuW5vJ5JLX9nh9bkaxH13+XKNZPsJ0YC8hq oea3jvsoPBOfWRXvpxY8ohmFwT0P9bkYkRfIhOg9L4GvmLmB6IGSaiP5BxHBKqdB0fepRPTyTiNCF f8MDIMLsxtZi9uxuiO0iYYP4WMbribWEWguQbdrcaDwwatJ3KRZreJJgnI7uL8J2cfxz7kl3j6jWb lH4R9mtlve4yTsij/YXX98eMXxYC3PlNqJXwMdM7TY6zT40+TWW5caRIAONFcRHgNdhyddbMfgkER 2xZ9SgXcAEdw2y14sZ7w==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jH5yS-0002QD-SF; Wed, 25 Mar 2020 13:21:36 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jH5yO-0002PV-R1 for linux-arm-kernel@lists.infradead.org; Wed, 25 Mar 2020 13:21:35 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E442B31B; Wed, 25 Mar 2020 06:21:31 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E6D813F71F; Wed, 25 Mar 2020 06:21:29 -0700 (PDT) Date: Wed, 25 Mar 2020 13:21:27 +0000 From: Mark Rutland To: Kees Cook Subject: Re: [PATCH v2 5/5] arm64: entry: Enable random_kstack_offset support Message-ID: <20200325132127.GB12236@lakrids.cambridge.arm.com> References: <20200324203231.64324-1-keescook@chromium.org> <20200324203231.64324-6-keescook@chromium.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200324203231.64324-6-keescook@chromium.org> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200325_062134_035842_3DFAD2B5 X-CRM114-Status: GOOD ( 19.82 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jann Horn , Ard Biesheuvel , Peter Zijlstra , Catalin Marinas , x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Alexander Potapenko , linux-arm-kernel@lists.infradead.org, Andy Lutomirski , kernel-hardening@lists.openwall.com, "Perla, Enrico" , Thomas Gleixner , Will Deacon , Elena Reshetova Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Mar 24, 2020 at 01:32:31PM -0700, Kees Cook wrote: > Allow for a randomized stack offset on a per-syscall basis, with roughly > 5 bits of entropy. > > Signed-off-by: Kees Cook Just to check, do you have an idea of the impact on arm64? Patch 3 had figures for x86 where it reads the TSC, and it's unclear to me how get_random_int() compares to that. Otherwise, this looks sound to me; I'd jsut like to know whether the overhead is in the same ballpark. Thanks Mark. > --- > arch/arm64/Kconfig | 1 + > arch/arm64/kernel/syscall.c | 10 ++++++++++ > 2 files changed, 11 insertions(+) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 0b30e884e088..4d5aa4959f72 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -127,6 +127,7 @@ config ARM64 > select HAVE_ARCH_MMAP_RND_BITS > select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT > select HAVE_ARCH_PREL32_RELOCATIONS > + select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET > select HAVE_ARCH_SECCOMP_FILTER > select HAVE_ARCH_STACKLEAK > select HAVE_ARCH_THREAD_STRUCT_WHITELIST > diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c > index a12c0c88d345..238dbd753b44 100644 > --- a/arch/arm64/kernel/syscall.c > +++ b/arch/arm64/kernel/syscall.c > @@ -5,6 +5,7 @@ > #include > #include > #include > +#include > #include > > #include > @@ -42,6 +43,8 @@ static void invoke_syscall(struct pt_regs *regs, unsigned int scno, > { > long ret; > > + add_random_kstack_offset(); > + > if (scno < sc_nr) { > syscall_fn_t syscall_fn; > syscall_fn = syscall_table[array_index_nospec(scno, sc_nr)]; > @@ -51,6 +54,13 @@ static void invoke_syscall(struct pt_regs *regs, unsigned int scno, > } > > regs->regs[0] = ret; > + > + /* > + * Since the compiler chooses a 4 bit alignment for the stack, > + * let's save one additional bit (9 total), which gets us up > + * near 5 bits of entropy. > + */ > + choose_random_kstack_offset(get_random_int() & 0x1FF); > } > > static inline bool has_syscall_work(unsigned long flags) > -- > 2.20.1 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel