From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752540AbXCZNZM (ORCPT ); Mon, 26 Mar 2007 09:25:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752568AbXCZNZM (ORCPT ); Mon, 26 Mar 2007 09:25:12 -0400 Received: from mx1.redhat.com ([66.187.233.31]:43204 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752540AbXCZNZK (ORCPT ); Mon, 26 Mar 2007 09:25:10 -0400 From: David Howells In-Reply-To: References: <20070326024143.a226c9b2.akpm@linux-foundation.org> <1174904637.32691.86.camel@roc-desktop> <6017.1174908318@redhat.com> <6791.1174909459@redhat.com> <11045.1174911764@redhat.com> To: Pekka J Enberg Cc: Andrew Morton , bryan.wu@analog.com, linux-kernel@vger.kernel.org, Hugh Dickins , Alan Cox Subject: Re: [PATCH -mm] Revoke core code: fix nommu arch compiling error bug X-Mailer: MH-E 8.0; nmh 1.1; GNU Emacs 22.0.50 Date: Mon, 26 Mar 2007 14:24:38 +0100 Message-ID: <22674.1174915478@redhat.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Pekka J Enberg wrote: > We don't touch private mappings at all as they're a snapshot to the inode > _before_ it was revoked. So private mappings don't really matter all: you > don't see any new data after it has been revoked nor do you flush anything > to the disk. Okay, so that's not a problem. > Well, assuming we would use revoke for things like SAK, this doesn't > really work out too well because all a malicious process has to is create > a shared mapping and they've effectively blocked the whole thing. In NOMMU-mode, there's probably[*] nothing stopping a malicious process running completely amok and changing stuff directly - even the kernel isn't guaranteed to be safe - so I wouldn't worry about such a case. [*] The FRV, for example, does have some limited protection capability - but it is really limited and not really useful in this case. > It's antisocial for sure but the only way to guarantee revoke() succeeds on > a NOMMU setup. Oh well, lets disable it for now and see if anyone even > wants revoke() for NOMMU. Agreed. David