Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754201AbZAFGVZ (ORCPT ); Tue, 6 Jan 2009 01:21:25 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751321AbZAFGVQ (ORCPT ); Tue, 6 Jan 2009 01:21:16 -0500 Received: from cantor2.suse.de ([195.135.220.15]:58618 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751167AbZAFGVP (ORCPT ); Tue, 6 Jan 2009 01:21:15 -0500 Date: Mon, 5 Jan 2009 22:19:46 -0800 From: Greg KH To: Mike Frysinger Cc: Robin Getz , viro@zeniv.linux.org.uk, linux-kernel@vger.kernel.org Subject: Re: debugfs & vfs file permission issue? Message-ID: <20090106061946.GA10026@suse.de> References: <200901052157.07306.rgetz@blackfin.uclinux.org> <20090106054858.GA9040@suse.de> <8bd0f97a0901052154w213f9a03oafdd07645b1b7dc7@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8bd0f97a0901052154w213f9a03oafdd07645b1b7dc7@mail.gmail.com> User-Agent: Mutt/1.5.16 (2007-06-09) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1626 Lines: 43 On Tue, Jan 06, 2009 at 12:54:58AM -0500, Mike Frysinger wrote: > On Tue, Jan 6, 2009 at 00:48, Greg KH wrote: > > On Mon, Jan 05, 2009 at 09:57:07PM -0500, Robin Getz wrote: > >> On 2.6.28-rc2, If I create a debugfs file with > >> > >> debugfs_create_x16("SPORT1_TX", 0200 , parent, 0xFFC00910); > > > > Um, are you are passing in a pointer to a known memory location > > properly? Why would it be ok for the kernel to directly read that > > location? > > it's a nommu system and the 0xffc00000+ addresses are always available Writable but not readable? Isn't hardware fun :) > >> Although the file shows up as write only (no read): > >> > >> root:/> ls -l /sys/kernel/debug/blackfin/SPORT/SPORT1_TX > >> --w------- 1 root root 0 Jan 1 > >> 2007 /sys/kernel/debug/blackfin/SPORT/SPORT1_TX > >> > >> root:/> cat /sys/kernel/debug/blackfin/SPORT/SPORT1_TX > >> > >> Still works - and causes the read to occur, which crashes :( > > > > You're root, you can do anything :) > > any thoughts on how to declare debugfs files that are read or write > only ? we'll have to add new helper functions or have it be a > parameter or declare our own debugfs file ? Just use debugfs_create_file() and use your own read/write functions to prevent a read or write from happening no matter what. No new debugfs infrastructure should be needed. good luck, greg k-h -- 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/