From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: [PATCH] tun: avoid owner checks on IFF_ATTACH_QUEUE Date: Thu, 10 Jan 2013 22:08:03 +0800 Message-ID: <50EECB43.8020405@redhat.com> References: <20130110113108.GF13451@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Stefan Hajnoczi , "David S. Miller" , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Paul Moore To: "Michael S. Tsirkin" Return-path: In-Reply-To: <20130110113108.GF13451@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 01/10/2013 07:31 PM, Michael S. Tsirkin wrote: > At the moment, we check owner when we enable queue in tun. > This seems redundant and will break some valid uses > where fd is passed around: I think TUNSETOWNER is there > to prevent others from attaching to a persistent device not > owned by them. Here the fd is already attached, > enabling/disabling queue is more like read/write. It also change the number of queues of the tuntap, maybe we should limit this. Note that if management layer does not call TUNSETOWNER, the check is just a nop. So if management layer want to limit the behavior, it's its duty to do this correctly. > Signed-off-by: Michael S. Tsirkin > > --- > > Note: this is unrelated to Stefan's bugfix. > > diff --git a/drivers/net/tun.c b/drivers/net/tun.c > index fbd106e..78e3225 100644 > --- a/drivers/net/tun.c > +++ b/drivers/net/tun.c > @@ -1789,10 +1792,8 @@ static int tun_set_queue(struct file *file, struct ifreq *ifr) > tun = tfile->detached; > if (!tun) > ret = -EINVAL; > - else if (tun_not_capable(tun)) > - ret = -EPERM; > else > ret = tun_attach(tun, file); > } else if (ifr->ifr_flags & IFF_DETACH_QUEUE) { > tun = rcu_dereference_protected(tfile->tun, > lockdep_rtnl_is_held());