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=-3.8 required=3.0 tests=BAYES_00, 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 BE75DC433E1 for ; Mon, 17 Aug 2020 08:23:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9EC1D20758 for ; Mon, 17 Aug 2020 08:23:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728190AbgHQIXu convert rfc822-to-8bit (ORCPT ); Mon, 17 Aug 2020 04:23:50 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([207.82.80.151]:25465 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727898AbgHQIXR (ORCPT ); Mon, 17 Aug 2020 04:23:17 -0400 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-180-lNRQs7-OMBKEt5epJ5rllg-1; Mon, 17 Aug 2020 09:23:12 +0100 X-MC-Unique: lNRQs7-OMBKEt5epJ5rllg-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Mon, 17 Aug 2020 09:23:11 +0100 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Mon, 17 Aug 2020 09:23:11 +0100 From: David Laight To: 'Christoph Hellwig' , Al Viro , Michael Ellerman , "x86@kernel.org" CC: Kees Cook , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-arch@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" Subject: RE: [PATCH 09/11] x86: remove address space overrides using set_fs() Thread-Topic: [PATCH 09/11] x86: remove address space overrides using set_fs() Thread-Index: AQHWdGicIkTuqnSld0yWphpVxhe9Oqk79IHw Date: Mon, 17 Aug 2020 08:23:11 +0000 Message-ID: <935d551809894d14965e430e05d21057@AcuMS.aculab.com> References: <20200817073212.830069-1-hch@lst.de> <20200817073212.830069-10-hch@lst.de> In-Reply-To: <20200817073212.830069-10-hch@lst.de> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0.001 X-Mimecast-Originator: aculab.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Christoph Hellwig > Sent: 17 August 2020 08:32 > > Stop providing the possibility to override the address space using > set_fs() now that there is no need for that any more. To properly > handle the TASK_SIZE_MAX checking for 4 vs 5-level page tables on > x86 a new alternative is introduced, which just like the one in > entry_64.S has to use the hardcoded virtual address bits to escape > the fact that TASK_SIZE_MAX isn't actually a constant when 5-level > page tables are enabled. .... > @@ -93,7 +69,7 @@ static inline bool pagefault_disabled(void); > #define access_ok(addr, size) \ > ({ \ > WARN_ON_IN_IRQ(); \ > - likely(!__range_not_ok(addr, size, user_addr_max())); \ > + likely(!__range_not_ok(addr, size, TASK_SIZE_MAX)); \ > }) Can't that always compare against a constant even when 5-levl page tables are enabled on x86-64? On x86-64 it can (probably) reduce to (addr | (addr + size)) < 0. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)