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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 0E0B2C433ED for ; Wed, 5 May 2021 08:37:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CCFEC611AC for ; Wed, 5 May 2021 08:37:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231987AbhEEIiw (ORCPT ); Wed, 5 May 2021 04:38:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44168 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231981AbhEEIio (ORCPT ); Wed, 5 May 2021 04:38:44 -0400 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C5B5CC06174A; Wed, 5 May 2021 01:37:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=jK0moekqG1xhMRv7+xXp4lJk9jp8uiNxobgiWKXh+5A=; b=jkvUVKohOf8O1K994UUXsnu1Gj pAAaW1jnaye2Wb2MFj/ciaGL47PIcPViHLq0CnU333G/XawQNPK0MV6jmzZ4iyBgSQMki6+TDvuy3 hBUKvCswsLWem6snP55iS3jVqkke/+1gG137r3Igj/sdeN6oBGiR5ejHqcP/5OYtpMBlxQlB0WvYZ XUmLfDJtEqZ3rlw81tUS47E6aBsOEjpbYfbPZzqkON39WlzByDrdH6PpKXhyVLiOTqB/200jKL5pv RtP0WEXVcHu+1wVhJHtq1jJEiB5kNS5Dmu64OI+dtC1CWvHBIwfvdgtby5nCAAbOX0JIxQC66ZV60 1Vbtr6cA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.94 #2 (Red Hat Linux)) id 1leD2B-000eI4-25; Wed, 05 May 2021 08:37:32 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 710D93001CD; Wed, 5 May 2021 10:37:29 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 57BA52D6DCEF9; Wed, 5 May 2021 10:37:29 +0200 (CEST) Date: Wed, 5 May 2021 10:37:29 +0200 From: Peter Zijlstra To: Kees Cook Cc: Rick Edgecombe , dave.hansen@intel.com, luto@kernel.org, linux-mm@kvack.org, x86@kernel.org, akpm@linux-foundation.org, linux-hardening@vger.kernel.org, kernel-hardening@lists.openwall.com, ira.weiny@intel.com, rppt@kernel.org, dan.j.williams@intel.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH RFC 0/9] PKS write protected page tables Message-ID: References: <20210505003032.489164-1-rick.p.edgecombe@intel.com> <202105042253.ECBBF6B6@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <202105042253.ECBBF6B6@keescook> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 04, 2021 at 11:25:31PM -0700, Kees Cook wrote: > It looks like PKS-protected page tables would be much like the > RO-protected text pages in the sense that there is already code in > the kernel to do things to make it writable, change text, and set it > read-only again (alternatives, ftrace, etc). We don't actually modify text by changing the mapping at all. We modify through a writable (but not executable) temporary alias on the page (on x86). Once a mapping is RX it will *never* be writable again (until we tear it all down).