From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-6.0 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI,SPF_HELO_NONE,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 2583F7D8AB for ; Mon, 1 Jul 2019 19:57:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726691AbfGAT5Q (ORCPT ); Mon, 1 Jul 2019 15:57:16 -0400 Received: from mga09.intel.com ([134.134.136.24]:12848 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726686AbfGAT5Q (ORCPT ); Mon, 1 Jul 2019 15:57:16 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 01 Jul 2019 12:57:15 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.63,440,1557212400"; d="scan'208";a="361947326" Received: from yyu32-desk1.sc.intel.com ([10.144.153.205]) by fmsmga005.fm.intel.com with ESMTP; 01 Jul 2019 12:57:15 -0700 Message-ID: Subject: Re: [RFC PATCH 3/3] Prevent user from writing to IBT bitmap. From: Yu-cheng Yu To: Andy Lutomirski Cc: X86 ML , "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , LKML , "open list:DOCUMENTATION" , Linux-MM , linux-arch , Linux API , Arnd Bergmann , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin Date: Mon, 01 Jul 2019 12:48:56 -0700 In-Reply-To: References: <20190628194158.2431-1-yu-cheng.yu@intel.com> <20190628194158.2431-3-yu-cheng.yu@intel.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.1-2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Sat, 2019-06-29 at 16:44 -0700, Andy Lutomirski wrote: > On Fri, Jun 28, 2019 at 12:50 PM Yu-cheng Yu wrote: > > > > The IBT bitmap is visiable from user-mode, but not writable. > > > > Signed-off-by: Yu-cheng Yu > > > > --- > > arch/x86/mm/fault.c | 7 +++++++ > > 1 file changed, 7 insertions(+) > > > > diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c > > index 59f4f66e4f2e..231196abb62e 100644 > > --- a/arch/x86/mm/fault.c > > +++ b/arch/x86/mm/fault.c > > @@ -1454,6 +1454,13 @@ void do_user_addr_fault(struct pt_regs *regs, > > * we can handle it.. > > */ > > good_area: > > +#define USER_MODE_WRITE (FAULT_FLAG_WRITE | FAULT_FLAG_USER) > > + if (((flags & USER_MODE_WRITE) == USER_MODE_WRITE) && > > + (vma->vm_flags & VM_IBT)) { > > + bad_area_access_error(regs, hw_error_code, address, vma); > > + return; > > + } > > + > > Just make the VMA have VM_WRITE and VM_MAYWRITE clear. No new code > like this should be required. Ok, I will work on that. Thanks, Yu-cheng