Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S267808AbUIGKQ6 (ORCPT ); Tue, 7 Sep 2004 06:16:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S267810AbUIGKQ5 (ORCPT ); Tue, 7 Sep 2004 06:16:57 -0400 Received: from ns.virtualhost.dk ([195.184.98.160]:7563 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S267808AbUIGKQn (ORCPT ); Tue, 7 Sep 2004 06:16:43 -0400 Date: Tue, 7 Sep 2004 12:15:29 +0200 From: Jens Axboe To: Andrew Morton Cc: paulus@samba.org, juhl-lkml@dif.dk, linux-kernel@vger.kernel.org Subject: Re: [PATCH] remember to check return value from __copy_to_user() in cdrom_read_cdda_old() Message-ID: <20040907101529.GO6323@suse.de> References: <20040907080223.GF6323@suse.de> <16701.32784.10441.884090@cargo.ozlabs.ibm.com> <20040907093437.GK6323@suse.de> <20040907025921.7f6a4139.akpm@osdl.org> <20040907100941.GN6323@suse.de> <20040907031258.15271794.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040907031258.15271794.akpm@osdl.org> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1785 Lines: 45 On Tue, Sep 07 2004, Andrew Morton wrote: > Jens Axboe wrote: > > > > On Tue, Sep 07 2004, Andrew Morton wrote: > > > Jens Axboe wrote: > > > > > > > > On Tue, Sep 07 2004, Paul Mackerras wrote: > > > > > Jens Axboe writes: > > > > > > > > > > > __copy_to_user is the unchecking version of copy_to_user. > > > > > > > > > > It doesn't range-check the address, but it does return non-zero > > > > > (number of bytes not copied) if it encounters a fault writing to the > > > > > user buffer. > > > > > > > > but it doesn't matter, if it returns non-zero then something happened > > > > between the access_ok() and the actual copy because the user app did > > > > something silly. so I don't care much really, I think the major point is > > > > the kernel will cope. > > > > > > > > you could remove the access_ok() and change it to a copy_to_user() > > > > instead, I don't care either way. it's the old and slow interface which > > > > really never is used unless things have gone wrong anyways. > > > > > > > > > > Sure, but at present if an application tries to read cdrom data to address > > > 0x00000000 (say), the kernel will return "success". It should return an > > > error code. (Actually, it should return a short read if any data was > > > transferred, but whatever). > > > > Because access_ok() isn't reliable? > > access_ok() simply checks that the address is in the 0x00000000 - > 0xbfffffff range. We can still get faults in that range. Ok, it's pretty useless then. -- Jens Axboe - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/