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=-13.9 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 635C0C433E9 for ; Thu, 3 Sep 2020 16:08:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3823720829 for ; Thu, 3 Sep 2020 16:08:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728382AbgICQIf (ORCPT ); Thu, 3 Sep 2020 12:08:35 -0400 Received: from pegase1.c-s.fr ([93.17.236.30]:8836 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727786AbgICQIc (ORCPT ); Thu, 3 Sep 2020 12:08:32 -0400 Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 4Bj5MH5XfvzB09ZM; Thu, 3 Sep 2020 18:08:27 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id AhUkCQsrRXgc; Thu, 3 Sep 2020 18:08:27 +0200 (CEST) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 4Bj5MH4CVtzB09ZK; Thu, 3 Sep 2020 18:08:27 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 73D218B806; Thu, 3 Sep 2020 18:08:28 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id 5YzyNRM3vKXH; Thu, 3 Sep 2020 18:08:28 +0200 (CEST) Received: from [192.168.4.90] (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id ECB968B803; Thu, 3 Sep 2020 18:08:20 +0200 (CEST) Subject: Re: [PATCH 14/14] powerpc: remove address space overrides using set_fs() To: Christoph Hellwig Cc: Linus Torvalds , Al Viro , Michael Ellerman , x86@kernel.org, linux-arch@vger.kernel.org, Kees Cook , linux-kernel@vger.kernel.org, Luis Chamberlain , linux-fsdevel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Alexey Dobriyan References: <20200903142242.925828-1-hch@lst.de> <20200903142242.925828-15-hch@lst.de> <20200903154909.GA23023@lst.de> <20200903155644.GA23521@lst.de> From: Christophe Leroy Message-ID: <7b895389-3da8-f634-4a13-82e533398ec5@csgroup.eu> Date: Thu, 3 Sep 2020 18:03:56 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <20200903155644.GA23521@lst.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Le 03/09/2020 à 17:56, Christoph Hellwig a écrit : > On Thu, Sep 03, 2020 at 05:49:09PM +0200, Christoph Hellwig wrote: >> On Thu, Sep 03, 2020 at 05:43:25PM +0200, Christophe Leroy wrote: >>> >>> >>> Le 03/09/2020 à 16:22, Christoph Hellwig a écrit : >>>> Stop providing the possibility to override the address space using >>>> set_fs() now that there is no need for that any more. >>>> >>>> Signed-off-by: Christoph Hellwig >>>> --- >>> >>> >>>> -static inline int __access_ok(unsigned long addr, unsigned long size, >>>> - mm_segment_t seg) >>>> +static inline bool __access_ok(unsigned long addr, unsigned long size) >>>> { >>>> - if (addr > seg.seg) >>>> - return 0; >>>> - return (size == 0 || size - 1 <= seg.seg - addr); >>>> + if (addr >= TASK_SIZE_MAX) >>>> + return false; >>>> + return size == 0 || size <= TASK_SIZE_MAX - addr; >>>> } >>> >>> You don't need to test size == 0 anymore. It used to be necessary because >>> of the 'size - 1', as size is unsigned. >>> >>> Now you can directly do >>> >>> return size <= TASK_SIZE_MAX - addr; >>> >>> If size is 0, this will always be true (because you already know that addr >>> is not >= TASK_SIZE_MAX >> >> True. What do you think of Linus' comment about always using the >> ppc32 version on ppc64 as well with this? I have nothing against it. That's only adding a substract, all args are already in registers so that will be in the noise for a modern CPU. > > i.e. something like this folded in: > > diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h > index 5363f7fc6dd06c..be070254e50943 100644 > --- a/arch/powerpc/include/asm/uaccess.h > +++ b/arch/powerpc/include/asm/uaccess.h > @@ -11,26 +11,14 @@ > #ifdef __powerpc64__ > /* We use TASK_SIZE_USER64 as TASK_SIZE is not constant */ > #define TASK_SIZE_MAX TASK_SIZE_USER64 > - > -/* > - * This check is sufficient because there is a large enough gap between user > - * addresses and the kernel addresses. > - */ > -static inline bool __access_ok(unsigned long addr, unsigned long size) > -{ > - return addr < TASK_SIZE_MAX && size < TASK_SIZE_MAX; > -} > - > #else > #define TASK_SIZE_MAX TASK_SIZE > +#endif > > static inline bool __access_ok(unsigned long addr, unsigned long size) > { > - if (addr >= TASK_SIZE_MAX) > - return false; > - return size == 0 || size <= TASK_SIZE_MAX - addr; > + return addr < TASK_SIZE_MAX && size <= TASK_SIZE_MAX - addr; > } > -#endif /* __powerpc64__ */ > > #define access_ok(addr, size) \ > (__chk_user_ptr(addr), \ > Christophe