Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753258AbaA0CHB (ORCPT ); Sun, 26 Jan 2014 21:07:01 -0500 Received: from mga09.intel.com ([134.134.136.24]:3465 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753130AbaA0CHA (ORCPT ); Sun, 26 Jan 2014 21:07:00 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.95,726,1384329600"; d="scan'208";a="444963875" Message-ID: <52E5BDF1.20107@intel.com> Date: Mon, 27 Jan 2014 10:01:21 +0800 From: Ren Qiaowei User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.1 MIME-Version: 1.0 To: Ingo Molnar CC: "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , "x86@kernel.org" , "linux-kernel@vger.kernel.org" , Peter Zijlstra , Linus Torvalds , Andrew Morton Subject: Re: [PATCH v3 3/4] x86, mpx: add prctl commands PR_MPX_INIT, PR_MPX_RELEASE References: <1390727338-20487-1-git-send-email-qiaowei.ren@intel.com> <1390727338-20487-4-git-send-email-qiaowei.ren@intel.com> <20140126090808.GA30987@gmail.com> <9E0BE1322F2F2246BD820DA9FC397ADE014F22A8@SHSMSX102.ccr.corp.intel.com> <20140126151422.GA5386@gmail.com> In-Reply-To: <20140126151422.GA5386@gmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/26/2014 11:14 PM, Ingo Molnar wrote: > > * Ren, Qiaowei wrote: > >> The size of one bound table is 4M bytes for 64bit, and 16K bytes for >> 32bit. It can not be accessed by user-space, and it will be accessed >> automatically by hardware. > > So, here's the bound-table allocation AFAICS: > > +static bool allocate_bt(unsigned long bd_entry) > +{ > + unsigned long bt_size = 1UL << (MPX_L2_BITS+MPX_L2_SHIFT); > + unsigned long bt_addr, old_val = 0; > + > + bt_addr = sys_mmap_pgoff(0, bt_size, PROT_READ | PROT_WRITE, > + MAP_ANONYMOUS | MAP_PRIVATE | MAP_POPULATE, -1, 0); > > What ensures that user-space cannot access (and in particular, modify) > the pages at bt_addr? It's a read-write anonymous mapping AFAICS. > Looks like that we can not be able to ensure this. I just mean that user-space doesn't know the bound tables, and it should not access them also. Thanks, Qiaowei -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/