From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932353Ab2LFX7w (ORCPT ); Thu, 6 Dec 2012 18:59:52 -0500 Received: from mx1.redhat.com ([209.132.183.28]:1686 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932077Ab2LFX7v (ORCPT ); Thu, 6 Dec 2012 18:59:51 -0500 Date: Thu, 6 Dec 2012 21:59:49 -0200 From: Marcelo Tosatti To: Alex Williamson Cc: kvm@vger.kernel.org, gleb@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 5/6] kvm: Re-introduce memslots->nmemslots Message-ID: <20121206235949.GA30775@amt.cnet> References: <20121203231912.3661.57179.stgit@bling.home> <20121203233936.3661.69261.stgit@bling.home> <20121205212629.GD20260@amt.cnet> <1354748573.3224.63.camel@bling.home> <20121206014507.GA9890@amt.cnet> <1354765897.3224.71.camel@bling.home> <20121206235848.GA30582@amt.cnet> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121206235848.GA30582@amt.cnet> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 06, 2012 at 09:58:48PM -0200, Marcelo Tosatti wrote: > On Wed, Dec 05, 2012 at 08:51:37PM -0700, Alex Williamson wrote: > > > > id_to_memslot seems like a good place to catch all the users since > > > > that's the only way to get a slot from a slot id after the array is > > > > sorted. We need to check both is the slot in bounds (EINVAL), but also > > > > is it allocated (ENOENT). id_to_memslot could both of these if we > > > > wanted to switch it to ERR_PTR. Thanks, > > > > > > > > Alex > > > > > > There should never be a reference to a slot out of bounds by KVM itself > > > (BUG_ON). Only userspace can attempt a reference to such slot. > > > > If I understand correctly, you're saying this last chunk is unique > > because kvm_get_dirty_log() is an internal interface and the test should > > be restricted to callers from userspace interfaces, namely > > kvm_vm_ioctl_get_dirty_log(). That sounds reasonable; book3s_pr seems > > to be the only caller that relies on kvm_get_dirty_log() validating the > > slot. Thanks, > > > > Alex > > Yep - so you can move the check to such userspace interfaces, and bug on > on WARN otherwise (in id_to_memslot). WARN_ON. The point is, if its not a valid condition, it should be explicitly so. > Does that make sense?? >