Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757909AbYAEVSb (ORCPT ); Sat, 5 Jan 2008 16:18:31 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757227AbYAEVSW (ORCPT ); Sat, 5 Jan 2008 16:18:22 -0500 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:42916 "EHLO amd.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756959AbYAEVSS (ORCPT ); Sat, 5 Jan 2008 16:18:18 -0500 Date: Sat, 5 Jan 2008 22:18:26 +0100 From: Pavel Machek To: Oliver Neukum Cc: nigel@nigel.suspend2.net, "Rafael J. Wysocki" , Kyle Moffett , Matthew Garrett , David Chinner , Jeremy Fitzhardinge , xfs-masters@oss.sgi.com, Linux Kernel Mailing List Subject: Re: freeze vs freezer Message-ID: <20080105211826.GB25341@elf.ucw.cz> References: <4744FD87.7010301@goop.org> <200801031215.07145.oliver@neukum.org> <477D5C4F.8050800@nigel.suspend2.net> <200801042154.08758.oliver@neukum.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200801042154.08758.oliver@neukum.org> X-Warning: Reading this can be dangerous to your mental health. 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 Content-Length: 2184 Lines: 49 On Fri 2008-01-04 21:54:06, Oliver Neukum wrote: > Am Donnerstag, 3. Januar 2008 23:06:07 schrieb Nigel Cunningham: > > Hi. > > > > Oliver Neukum wrote: > > > Am Donnerstag, 3. Januar 2008 10:52:53 schrieb Nigel Cunningham: > > >> Hi. > > >> > > >> Oliver Neukum wrote: > > >>> Am Donnerstag 03 Januar 2008 schrieb Nigel Cunningham: > > >>>> On top of this, I made a (too simple at the moment) freeze_filesystems > > >>>> function which iterates through &super_blocks in reverse order, freezing > > >>>> fuse filesystems or ordinary ones. I say 'too simple' because it doesn't > > >>>> currently allow for the possibility of someone mounting (say) ext3 on > > >>>> fuse, but that would just be an extension of what's already done. > > >>> How do you deal with fuse server tasks using other fuse filesystems? > > >> Since they're frozen in reverse order, the dependant one would be frozen > > >> first. > > > > > > Say I do: > > > > > > a) mount fuse on /tmp/first > > > b) mount fuse on /tmp/second > > > > > > Then the server task for (a) does "ls /tmp/second". So it will be frozen, > > > right? How do you then freeze (a)? And keep in mind that the server task > > > may have forked. > > > > I guess I should first ask, is this a real life problem or a > > hypothetical twisted web? I don't see why you would want to make two > > filesystems interdependent - it sounds like the way to create livelock > > and deadlocks in normal use, before we even begin to think about > > hibernating. > > Good questions. I personally don't use fuse, but I do care about power > management. The problem I see is that an unprivileged user could make > that dependency, even inadvertedly. Other problem is that unprivileged user can do it with evil intent. So called "denial-of-service" attack. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- 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/