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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,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 CFD3DC2D0DB for ; Wed, 22 Jan 2020 17:54:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ACB4A20663 for ; Wed, 22 Jan 2020 17:54:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=c-s.fr header.i=@c-s.fr header.b="OcJlBYzu" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726005AbgAVRyr (ORCPT ); Wed, 22 Jan 2020 12:54:47 -0500 Received: from pegase1.c-s.fr ([93.17.236.30]:48676 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725802AbgAVRyr (ORCPT ); Wed, 22 Jan 2020 12:54:47 -0500 Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 482tMm3lzRz9vBf2; Wed, 22 Jan 2020 18:54:44 +0100 (CET) Authentication-Results: localhost; dkim=pass reason="1024-bit key; insecure key" header.d=c-s.fr header.i=@c-s.fr header.b=OcJlBYzu; dkim-adsp=pass; dkim-atps=neutral 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 g55D7HPV3Pwg; Wed, 22 Jan 2020 18:54:44 +0100 (CET) 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 482tMm2SL9z9vBf1; Wed, 22 Jan 2020 18:54:44 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=c-s.fr; s=mail; t=1579715684; bh=nMZdRf5UsRj5KxQzwPP0NxCJ+9fa/JNI7E3shGKwtEs=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=OcJlBYzuayKTBlwDBdHG6QFeB0VoE/H+bzD9dU4M5bNP7OWUZKU4CVf0g6xmdG17n aDVEV8uPTBOJLj3L7ro5dOR/K2G0KeM7H1aC/PuOC8xLvG2mvLfW1Nobjbnwkl2FQU I6xJXWlceBU7CM1zDVJfem12s6jlYfllbGHsPocg= Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 029598B810; Wed, 22 Jan 2020 18:54:46 +0100 (CET) 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 fO2Q8JMqvBdc; Wed, 22 Jan 2020 18:54:45 +0100 (CET) Received: from [192.168.4.90] (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 565C88B7FE; Wed, 22 Jan 2020 18:54:45 +0100 (CET) Subject: Re: [PATCH v1 1/6] fs/readdir: Fix filldir() and filldir64() use of user_access_begin() To: Al Viro , Linus Torvalds Cc: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Andrew Morton , Linux Kernel Mailing List , linuxppc-dev , linux-fsdevel , Linux-MM References: <20200122174129.GH23230@ZenIV.linux.org.uk> From: Christophe Leroy Message-ID: Date: Wed, 22 Jan 2020 18:54:45 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.9.1 MIME-Version: 1.0 In-Reply-To: <20200122174129.GH23230@ZenIV.linux.org.uk> 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 22/01/2020 à 18:41, Al Viro a écrit : > On Wed, Jan 22, 2020 at 08:13:12AM -0800, Linus Torvalds wrote: >> On Wed, Jan 22, 2020 at 5:00 AM Christophe Leroy >> wrote: >>> >>> Modify filldir() and filldir64() to request the real area they need >>> to get access to. >> >> Not like this. >> >> This makes the situation for architectures like x86 much worse, since >> you now use "put_user()" for the previous dirent filling. Which does >> that expensive user access setup/teardown twice again. >> >> So either you need to cover both the dirent's with one call, or you >> just need to cover the whole (original) user buffer passed in. But not >> this unholy mixing of both unsafe_put_user() and regular put_user(). > > I would suggest simply covering the range from dirent->d_off to > buf->current_dir->d_name[namelen]; they are going to be close to > each other and we need those addresses anyway... > In v2, I'm covering from the beginning of parent dirent to the end of current dirent. Christophe