From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750878AbWJGLXO (ORCPT ); Sat, 7 Oct 2006 07:23:14 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750887AbWJGLXO (ORCPT ); Sat, 7 Oct 2006 07:23:14 -0400 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:26387 "EHLO spitz.ucw.cz") by vger.kernel.org with ESMTP id S1750878AbWJGLXN (ORCPT ); Sat, 7 Oct 2006 07:23:13 -0400 Date: Sat, 7 Oct 2006 11:23:01 +0000 From: Pavel Machek To: Michael Buesch Cc: Alan Cox , linux-kernel Subject: Re: Really good idea to allow mmap(0, FIXED)? Message-ID: <20061007112301.GB4277@ucw.cz> References: <200610052059.11714.mb@bu3sch.de> <1160085480.1607.32.camel@localhost.localdomain> <200610061644.33267.mb@bu3sch.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200610061644.33267.mb@bu3sch.de> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi! > > > > Besides that, I currently don't see a valid reason to mmap address 0. > > > > > > Comments? > > > > User zero is not neccessarily mapped at kernel zero so your argument > > isn't portable either. > > Eh, so what about the following. > We _have_ arches which map user zero to kernel zero. What about > specialcasing that on a per-arch case. So remapping user zero to > something else in kernel. Just add some magic constant on architectures you care about... make user 0 start at 4mb in kernel... and you get your security hardened kernel w/o breaking dosemu. All you need is to create a patch :-) -- Thanks for all the (sleeping) penguins.