From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932443AbbFQOcO (ORCPT ); Wed, 17 Jun 2015 10:32:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46787 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932375AbbFQOcF (ORCPT ); Wed, 17 Jun 2015 10:32:05 -0400 Date: Wed, 17 Jun 2015 16:32:02 +0200 From: "Michael S. Tsirkin" To: Paolo Bonzini Cc: Igor Mammedov , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Subject: Re: [PATCH 3/5] vhost: support upto 509 memory regions Message-ID: <20150617163028-mutt-send-email-mst@redhat.com> References: <20150617092910-mutt-send-email-mst@redhat.com> <20150617105421.71751f44@nial.brq.redhat.com> <20150617110711-mutt-send-email-mst@redhat.com> <20150617123742.5c3fec30@nial.brq.redhat.com> <20150617123842-mutt-send-email-mst@redhat.com> <20150617134803.5a03d04e@nial.brq.redhat.com> <20150617134848-mutt-send-email-mst@redhat.com> <20150617142339.6e6deb12@nial.brq.redhat.com> <20150617151030-mutt-send-email-mst@redhat.com> <5581742C.9060100@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5581742C.9060100@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 17, 2015 at 03:20:44PM +0200, Paolo Bonzini wrote: > > > On 17/06/2015 15:13, Michael S. Tsirkin wrote: > > > > Considering userspace can be malicious, I guess yes. > > > I don't think it's a valid concern in this case, > > > setting limit back from 509 to 64 will not help here in any way, > > > userspace still can create as many vhost instances as it needs > > > to consume memory it desires. > > > > Not really since vhost char device isn't world-accessible. > > It's typically opened by a priveledged tool, the fd is > > then passed to an unpriveledged userspace, or permissions dropped. > > Then what's the concern anyway? > > Paolo Each fd now ties up 16K of kernel memory. It didn't use to, so priveledged tool could safely give the unpriveledged userspace a ton of these fds. -- MST