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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 D7CC9C74A42 for ; Thu, 11 Jul 2019 07:16:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A5E8D208E4 for ; Thu, 11 Jul 2019 07:16:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728205AbfGKHQm (ORCPT ); Thu, 11 Jul 2019 03:16:42 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:49141 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728104AbfGKHQm (ORCPT ); Thu, 11 Jul 2019 03:16:42 -0400 Received: from [5.158.153.55] (helo=nanos.guests.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1hlTJh-00006C-Pb; Thu, 11 Jul 2019 09:16:33 +0200 Date: Thu, 11 Jul 2019 09:16:19 +0200 (CEST) From: Thomas Gleixner To: Nadav Amit cc: Jiri Kosina , Peter Zijlstra , Xi Ruoyao , Kees Cook , Linus Torvalds , Ingo Molnar , Linux List Kernel Mailing , Borislav Petkov , Len Brown , Andrew Morton , "Rafael J. Wysocki" , Tony Luck , Bob Moore , Erik Schmauss , Josh Poimboeuf , Daniel Bristot de Oliveira Subject: Re: [GIT PULL] x86/topology changes for v5.3 In-Reply-To: <89EBC357-BEAC-4252-915F-E183C2D350C4@vmware.com> Message-ID: References: <201907091727.91CC6C72D8@keescook> <1ad2de95e694a29909801d022fe2d556df9a4bd5.camel@mengyan1223.wang> <768463eb26a2feb0fcc374fd7f9cc28b96976917.camel@mengyan1223.wang> <20190710134433.GN3402@hirez.programming.kicks-ass.net> <89EBC357-BEAC-4252-915F-E183C2D350C4@vmware.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 11 Jul 2019, Nadav Amit wrote: > > On Jul 10, 2019, at 7:22 AM, Jiri Kosina wrote: > > > > On Wed, 10 Jul 2019, Peter Zijlstra wrote: > > > >> If we mark the key as RO after init, and then try and modify the key to > >> link module usage sites, things might go bang as described. > >> > >> Thanks! > >> > >> > >> diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c > >> index 27d7864e7252..5bf7a8354da2 100644 > >> --- a/arch/x86/kernel/cpu/common.c > >> +++ b/arch/x86/kernel/cpu/common.c > >> @@ -366,7 +366,7 @@ static __always_inline void setup_umip(struct cpuinfo_x86 *c) > >> cr4_clear_bits(X86_CR4_UMIP); > >> } > >> > >> -DEFINE_STATIC_KEY_FALSE_RO(cr_pinning); > >> +DEFINE_STATIC_KEY_FALSE(cr_pinning); > > > > Good catch, I guess that is going to fix it. > > > > At the same time though, it sort of destroys the original intent of Kees' > > patch, right? The exploits will just have to call static_key_disable() > > prior to calling native_write_cr4() again, and the protection is gone. > > Even with DEFINE_STATIC_KEY_FALSE_RO(), I presume you can just call > set_memory_rw(), make the page that holds the key writable, and then call > static_key_disable(), followed by a call to native_write_cr4(). That's true, but it's not worth the trouble. Thanks, tglx