From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx1-b.sourceforge.net ([10.3.1.91] helo=mail.sourceforge.net) by sc8-sf-list1-new.sourceforge.net with esmtp (Exim 4.43) id 1JqVNz-00086e-NI for user-mode-linux-devel@lists.sourceforge.net; Mon, 28 Apr 2008 08:35:24 -0700 Received: from [198.99.130.12] (helo=saraswathi.solana.com) by mail.sourceforge.net with esmtps (TLSv1:AES256-SHA:256) (Exim 4.44) id 1JqVNo-0004AU-4p for user-mode-linux-devel@lists.sourceforge.net; Mon, 28 Apr 2008 08:35:17 -0700 Date: Mon, 28 Apr 2008 11:29:40 -0400 From: Jeff Dike Message-ID: <20080428152940.GA7465@c2.user-mode-linux.org> References: <20080425175608.GA11182@c2.user-mode-linux.org> <20080426.163132.194697674.xiyou.wangcong@gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20080426.163132.194697674.xiyou.wangcong@gmail.com> Subject: Re: [uml-devel] [PATCH 6/19] UML - hppfs fixes List-Id: The user-mode Linux development list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: user-mode-linux-devel-bounces@lists.sourceforge.net Errors-To: user-mode-linux-devel-bounces@lists.sourceforge.net To: WANG Cong Cc: akpm@osdl.org, linux-kernel@vger.kernel.org, user-mode-linux-devel@lists.sourceforge.net On Sat, Apr 26, 2008 at 04:31:32PM +0800, WANG Cong wrote: > > + rem = copy_to_user(buf, &data->contents[off], count); > > + *ppos += count - rem; > > + if (rem > 0) > > + return -EFAULT; > > Could you please explain why check 'rem' after using it here? Actually, this isn't as wrong as it looks. copy_to_user returns what hasn't been copied (rem == remaining). So, I think the mistake is to return -EFAULT here. Returning the short count would be right, unless rem == count, in which case we return -EFAULT. Jeff -- Work email - jdike at linux dot intel dot com ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935764AbYD1PgS (ORCPT ); Mon, 28 Apr 2008 11:36:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S934077AbYD1Pf5 (ORCPT ); Mon, 28 Apr 2008 11:35:57 -0400 Received: from saraswathi.solana.com ([198.99.130.12]:55633 "EHLO saraswathi.solana.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933996AbYD1Pf4 (ORCPT ); Mon, 28 Apr 2008 11:35:56 -0400 Date: Mon, 28 Apr 2008 11:29:40 -0400 From: Jeff Dike To: WANG Cong Cc: akpm@osdl.org, linux-kernel@vger.kernel.org, user-mode-linux-devel@lists.sourceforge.net Subject: Re: [PATCH 6/19] UML - hppfs fixes Message-ID: <20080428152940.GA7465@c2.user-mode-linux.org> References: <20080425175608.GA11182@c2.user-mode-linux.org> <20080426.163132.194697674.xiyou.wangcong@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080426.163132.194697674.xiyou.wangcong@gmail.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Apr 26, 2008 at 04:31:32PM +0800, WANG Cong wrote: > > + rem = copy_to_user(buf, &data->contents[off], count); > > + *ppos += count - rem; > > + if (rem > 0) > > + return -EFAULT; > > Could you please explain why check 'rem' after using it here? Actually, this isn't as wrong as it looks. copy_to_user returns what hasn't been copied (rem == remaining). So, I think the mistake is to return -EFAULT here. Returning the short count would be right, unless rem == count, in which case we return -EFAULT. Jeff -- Work email - jdike at linux dot intel dot com