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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 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 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 Kernel Mailing List , Linux-MM , Paul Mackerras , linux-fsdevel , Andrew Morton , linuxppc-dev Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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