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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 0EAF3C169C4 for ; Wed, 6 Feb 2019 17:41:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DB511218C3 for ; Wed, 6 Feb 2019 17:41:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730319AbfBFRlP (ORCPT ); Wed, 6 Feb 2019 12:41:15 -0500 Received: from mail.kernel.org ([198.145.29.99]:51640 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730103AbfBFRlN (ORCPT ); Wed, 6 Feb 2019 12:41:13 -0500 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4175C20B1F; Wed, 6 Feb 2019 17:41:11 +0000 (UTC) Date: Wed, 6 Feb 2019 12:41:08 -0500 From: Steven Rostedt To: Nadav Amit Cc: Rick Edgecombe , Andy Lutomirski , Ingo Molnar , LKML , X86 ML , "H. Peter Anvin" , Thomas Gleixner , Borislav Petkov , Dave Hansen , Peter Zijlstra , Damian Tometzki , linux-integrity , LSM List , Andrew Morton , Kernel Hardening , Linux-MM , Will Deacon , Ard Biesheuvel , Kristen Carlson Accardi , deneen.t.dock@intel.com Subject: Re: [PATCH 08/17] x86/ftrace: set trampoline pages as executable Message-ID: <20190206124108.07eef568@gandalf.local.home> In-Reply-To: <5DFA1E3C-A335-4C4B-A86F-904A6CF6D871@gmail.com> References: <20190117003259.23141-1-rick.p.edgecombe@intel.com> <20190117003259.23141-9-rick.p.edgecombe@intel.com> <20190206112213.2ec9dd5c@gandalf.local.home> <5DFA1E3C-A335-4C4B-A86F-904A6CF6D871@gmail.com> X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 6 Feb 2019 09:33:35 -0800 Nadav Amit wrote: > >> /* Copy ftrace_caller onto the trampoline memory */ > >> ret = probe_kernel_read(trampoline, (void *)start_offset, size); > >> @@ -818,6 +820,13 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) > >> /* ALLOC_TRAMP flags lets us know we created it */ > >> ops->flags |= FTRACE_OPS_FL_ALLOC_TRAMP; > >> > >> + /* > >> + * Module allocation needs to be completed by making the page > >> + * executable. The page is still writable, which is a security hazard, > >> + * but anyhow ftrace breaks W^X completely. > >> + */ > > > > Perhaps we should set the page to non writable after the page is > > updated? And set it to writable only when we need to update it. > > You remember that I sent you a patch that changed all these writes into > text_poke() and you said that I should defer it until this series is merged? > And I notice that it is set to RO after this call anyway. -- Steve