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Commit addf8fc4 authored by Jason Wang's avatar Jason Wang Committed by David S. Miller
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tuntap: correctly wake up process during uninit 



We used to check dev->reg_state against NETREG_REGISTERED after each
time we are woke up. But after commit 9e641bdc ("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: 9e641bdc ("net-tun: restructure tun_do_read for better
sleep/wakeup efficiency")
Cc: Eric Dumazet <edumazet@google.com>
Cc: Xi Wang <xii@google.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Acked-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7fd3c56d

drivers/net/tun.c

+3 −3
Original line number Diff line number Diff line
@@ -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++;
@@ -1491,9 +1494,6 @@ static ssize_t tun_do_read(struct tun_struct *tun, struct tun_file *tfile, 
	if (!iov_iter_count(to))

		return 0;



	if (tun->dev->reg_state != NETREG_REGISTERED)

		return -EIO;



	/* Read frames from queue */

	skb = __skb_recv_datagram(tfile->socket.sk, noblock ? MSG_DONTWAIT : 0,

				  &peeked, &off, &err);