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=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 3E47BC433DF for ; Thu, 27 Aug 2020 09:39:54 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B2F1120738 for ; Thu, 27 Aug 2020 09:39:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B2F1120738 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 4Bcd4714gZzDqmf for ; Thu, 27 Aug 2020 19:39:51 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=none (no SPF record) smtp.mailfrom=lst.de (client-ip=213.95.11.211; helo=verein.lst.de; envelope-from=hch@lst.de; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=lst.de Received: from verein.lst.de (verein.lst.de [213.95.11.211]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4Bcd1v5t7nzDqg1 for ; Thu, 27 Aug 2020 19:37:54 +1000 (AEST) Received: by verein.lst.de (Postfix, from userid 2407) id 8281168B02; Thu, 27 Aug 2020 11:37:48 +0200 (CEST) Date: Thu, 27 Aug 2020 11:37:48 +0200 From: 'Christoph Hellwig' To: David Laight Subject: Re: [PATCH 09/11] x86: remove address space overrides using set_fs() Message-ID: <20200827093748.GA13887@lst.de> References: <20200817073212.830069-1-hch@lst.de> <20200817073212.830069-10-hch@lst.de> <935d551809894d14965e430e05d21057@AcuMS.aculab.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <935d551809894d14965e430e05d21057@AcuMS.aculab.com> User-Agent: Mutt/1.5.17 (2007-11-01) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "linux-arch@vger.kernel.org" , Kees Cook , "x86@kernel.org" , "linux-kernel@vger.kernel.org" , Al Viro , "linux-fsdevel@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , 'Christoph Hellwig' Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Mon, Aug 17, 2020 at 08:23:11AM +0000, David Laight wrote: > 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. I'll leave that to the x86 maintainers as a future cleanup if wanted.