From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: [PATCH net] tuntap: correctly wake up process during uninit Date: Thu, 19 May 2016 13:35:03 +0800 Message-ID: <573D5087.6070308@redhat.com> References: <1463569097-3528-1-git-send-email-jasowang@redhat.com> <1463576494.18194.94.camel@edumazet-glaptop3.roam.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Eric Dumazet , Xi Wang , "Michael S . Tsirkin" To: Eric Dumazet Return-path: In-Reply-To: <1463576494.18194.94.camel@edumazet-glaptop3.roam.corp.google.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 2016=E5=B9=B405=E6=9C=8818=E6=97=A5 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 use= s >> 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 t= he >> 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 unini= t. >> >> 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 *d= ev) > for (i =3D 0; i < n; i++) { > tfile =3D rtnl_dereference(tun->tfiles[i]); > BUG_ON(!tfile); > + tfile->socket.sk->sk_shutdown =3D 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 =3D 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, str= uct file *file, bool skip_filte > goto out; > } > tfile->queue_index =3D tun->numqueues; > + tfile->socket.sk->sk_shutdown &=3D ~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 !=3D NETREG_REGISTERED) return -EIO;" > check still needed then ? > > Thanks. > > No need since we've check tun before, will remove this in V2. Thanks