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")
<nit : no newline before Fixes: and other parts>
>
> Cc: Eric Dumazet <eduma...@google.com>
> Cc: Xi Wang <x...@google.com>
> Cc: Michael S. Tsirkin <m...@redhat.com>
> Signed-off-by: Jason Wang <jasow...@redhat.com>
> ---
> 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.
