From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752265AbcESFfM (ORCPT ); Thu, 19 May 2016 01:35:12 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40431 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751399AbcESFfJ (ORCPT ); Thu, 19 May 2016 01:35:09 -0400 Subject: Re: [PATCH net] tuntap: correctly wake up process during uninit To: Eric Dumazet References: <1463569097-3528-1-git-send-email-jasowang@redhat.com> <1463576494.18194.94.camel@edumazet-glaptop3.roam.corp.google.com> Cc: davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Eric Dumazet , Xi Wang , "Michael S . Tsirkin" From: Jason Wang Message-ID: <573D5087.6070308@redhat.com> Date: Thu, 19 May 2016 13:35:03 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.2 MIME-Version: 1.0 In-Reply-To: <1463576494.18194.94.camel@edumazet-glaptop3.roam.corp.google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Thu, 19 May 2016 05:35:09 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2016年05月18日 21:01, Eric Dumazet wrote: > On Wed, 2016-05-18 at 18:58 +0800, Jason Wang wrote: >> We used to check dev->reg_state against NETREG_REGISTERED after each >> time we are woke up. But after commit 9e641bdcfa4e ("net-tun: >> restructure tun_do_read for better sleep/wakeup efficiency"), it uses >> skb_recv_datagram() which does not check dev->reg_state. This will >> result if we delete a tun/tap device after a process is blocked in the >> reading. The device will wait for the reference count which was held >> by that process for ever. >> >> Fixes this by using RCV_SHUTDOWN which will be checked during >> sk_recv_datagram() before trying to wake up the process during uninit. >> >> Fixes: 9e641bdcfa4e ("net-tun: restructure tun_do_read for better >> sleep/wakeup efficiency") > Ok. > Cc: Eric Dumazet > Cc: Xi Wang > Cc: Michael S. Tsirkin > Signed-off-by: Jason Wang > --- > The patch is needed for -stable. > --- > drivers/net/tun.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/net/tun.c b/drivers/net/tun.c > index 425e983..752d849 100644 > --- a/drivers/net/tun.c > +++ b/drivers/net/tun.c > @@ -580,11 +580,13 @@ static void tun_detach_all(struct net_device *dev) > for (i = 0; i < n; i++) { > tfile = rtnl_dereference(tun->tfiles[i]); > BUG_ON(!tfile); > + tfile->socket.sk->sk_shutdown = RCV_SHUTDOWN; > tfile->socket.sk->sk_data_ready(tfile->socket.sk); > RCU_INIT_POINTER(tfile->tun, NULL); > --tun->numqueues; > } > list_for_each_entry(tfile, &tun->disabled, next) { > + tfile->socket.sk->sk_shutdown = RCV_SHUTDOWN; > tfile->socket.sk->sk_data_ready(tfile->socket.sk); > RCU_INIT_POINTER(tfile->tun, NULL); > } > @@ -641,6 +643,7 @@ static int tun_attach(struct tun_struct *tun, struct file *file, bool skip_filte > goto out; > } > tfile->queue_index = tun->numqueues; > + tfile->socket.sk->sk_shutdown &= ~RCV_SHUTDOWN; > rcu_assign_pointer(tfile->tun, tun); > rcu_assign_pointer(tun->tfiles[tun->numqueues], tfile); > tun->numqueues++; > Is the "if (tun->dev->reg_state != NETREG_REGISTERED) return -EIO;" > check still needed then ? > > Thanks. > > No need since we've check tun before, will remove this in V2. Thanks