From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760822AbYDSOnz (ORCPT ); Sat, 19 Apr 2008 10:43:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751245AbYDSOnp (ORCPT ); Sat, 19 Apr 2008 10:43:45 -0400 Received: from ozlabs.org ([203.10.76.45]:50394 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750776AbYDSOno (ORCPT ); Sat, 19 Apr 2008 10:43:44 -0400 From: Rusty Russell To: Andrew Morton Subject: Re: [PATCH 5/5] tun: vringfd xmit support. Date: Sun, 20 Apr 2008 00:41:43 +1000 User-Agent: KMail/1.9.9 Cc: netdev@vger.kernel.org, Max Krasnyansky , virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org References: <200804181433.48488.rusty@rustcorp.com.au> <200804190115.15983.rusty@rustcorp.com.au> <20080418120634.986e30f1.akpm@linux-foundation.org> In-Reply-To: <20080418120634.986e30f1.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200804200041.43969.rusty@rustcorp.com.au> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Saturday 19 April 2008 05:06:34 Andrew Morton wrote: > On Sat, 19 Apr 2008 01:15:15 +1000 Rusty Russell wrote: > > > What is the maximum numbet of pages which an unpriviliged user can > > > concurrently pin with this code? > > > > Since only root can open the tun device, it's currently OK. The old code > > kmalloced and copied: is there some mm-fu reason why pinning userspace > > memory is worse? > > We generally try to avoid it - it allows users to dos the box. My question is: is pinning a page worse than allocating a (kernel) page in some way? Cheers, Rusty.