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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=unavailable 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 C250AC04AB6 for ; Mon, 3 Jun 2019 07:44:41 +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 7F3A127CF1 for ; Mon, 3 Jun 2019 07:44:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7F3A127CF1 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 lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 45HRsM2vP9zDqSg for ; Mon, 3 Jun 2019 17:44:39 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=none (mailfrom) smtp.mailfrom=lst.de (client-ip=213.95.11.211; helo=newverein.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 newverein.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 45HRpF2PTpzDqNx for ; Mon, 3 Jun 2019 17:41:50 +1000 (AEST) Received: by newverein.lst.de (Postfix, from userid 2407) id B4E2E67358; Mon, 3 Jun 2019 09:41:21 +0200 (CEST) Date: Mon, 3 Jun 2019 09:41:21 +0200 From: Christoph Hellwig To: Linus Torvalds Subject: Re: [PATCH 03/16] mm: simplify gup_fast_permitted Message-ID: <20190603074121.GA22920@lst.de> References: <20190601074959.14036-1-hch@lst.de> <20190601074959.14036-4-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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: Rich Felker , Yoshinori Sato , Linux-sh list , James Hogan , the arch/x86 maintainers , Khalid Aziz , Nicholas Piggin , "David S. Miller" , Linux-MM , Paul Burton , Paul Mackerras , Andrey Konovalov , sparclinux@vger.kernel.org, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Christoph Hellwig , Linux List Kernel Mailing Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Sat, Jun 01, 2019 at 09:14:17AM -0700, Linus Torvalds wrote: > On Sat, Jun 1, 2019 at 12:50 AM Christoph Hellwig wrote: > > > > Pass in the already calculated end value instead of recomputing it, and > > leave the end > start check in the callers instead of duplicating them > > in the arch code. > > Good cleanup, except it's wrong. > > > - if (nr_pages <= 0) > > + if (end < start) > > return 0; > > You moved the overflow test to generic code - good. > > You removed the sign and zero test on nr_pages - bad. I only removed a duplicate of it. The full (old) code in get_user_pages_fast() looks like this: if (nr_pages <= 0) return 0; if (unlikely(!access_ok((void __user *)start, len))) return -EFAULT; if (gup_fast_permitted(start, nr_pages)) {