From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030393AbWGMVXR (ORCPT ); Thu, 13 Jul 2006 17:23:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030398AbWGMVXR (ORCPT ); Thu, 13 Jul 2006 17:23:17 -0400 Received: from e33.co.us.ibm.com ([32.97.110.151]:29340 "EHLO e33.co.us.ibm.com") by vger.kernel.org with ESMTP id S1030393AbWGMVXR (ORCPT ); Thu, 13 Jul 2006 17:23:17 -0400 Date: Thu, 13 Jul 2006 16:22:18 -0500 From: "Serge E. Hallyn" To: "Eric W. Biederman" Cc: Cedric Le Goater , linux-kernel@vger.kernel.org, Andrew Morton , Kirill Korotaev , Andrey Savochkin , Herbert Poetzl , Sam Vilain , "Serge E. Hallyn" , Dave Hansen Subject: Re: [PATCH -mm 5/7] add user namespace Message-ID: <20060713212218.GA2169@sergelap.austin.ibm.com> References: <20060711075051.382004000@localhost.localdomain> <20060711075420.937831000@localhost.localdomain> <44B50088.1010103@fr.ibm.com> <44B684A5.2040008@fr.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Quoting Eric W. Biederman (ebiederm@xmission.com): > >> keys are essentially security credentials for something besides the > >> local kernel. Think kerberos tickets. That makes the keys the > >> obvious place to say what uid you are in a different user namespace > >> and similar things. > > > > what about performance ? wouldn't that slow the checking ? > > It needs to be looked at, but it shouldn't slow the same namespace > case, How so? The processesing is the same. > and permission checking is largely a slow path issue. So a little > overhead at open time is preferred to overhead after you get the file > open. Unsure which approach has overhead after file open... -serge