From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756532AbYFEP6f (ORCPT ); Thu, 5 Jun 2008 11:58:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753636AbYFEP6Y (ORCPT ); Thu, 5 Jun 2008 11:58:24 -0400 Received: from waste.org ([66.93.16.53]:49565 "EHLO waste.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753477AbYFEP6Y (ORCPT ); Thu, 5 Jun 2008 11:58:24 -0400 Subject: Re: [PATCH 1/5] pagemap: Modify add_to_pagemap to use copy_to_user instead of put_user. From: Matt Mackall To: Thomas Tuttle Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org In-Reply-To: <4ca0a85e0806050804q4c164105uc386dcae2ccd21d@mail.gmail.com> References: <4ca0a85e0806050804q4c164105uc386dcae2ccd21d@mail.gmail.com> Content-Type: text/plain Date: Thu, 05 Jun 2008 10:57:57 -0500 Message-Id: <1212681477.3953.154.camel@calx> Mime-Version: 1.0 X-Mailer: Evolution 2.12.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2008-06-05 at 11:04 -0400, Thomas Tuttle wrote: > While fiddling with pagemap, I discovered a bug in add_to_pagemap. > When it is copying an entry that is not at the end of the buffer, it > uses put_user to copy a u64 into a char* buffer. The problem is that > put_user determines how much to copy based on the size of the > *destination*, not the source, so it only copied one byte. To fix > this, I replaced the call to put_user with a call to copy_to_user, as > is used when copying the last (possibly partial) PFN into the buffer. This looks fine to me, so: Acked-by: Matt Mackall But your 3/5 undoes this, right? So we should just take one or the other route. While I like going the simplifying route, it's not very pretty from the user interface point of view. But it does have plenty of precedent in direct-I/O-like things. -- Mathematics is the supreme nostalgia of our time.