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Commit d23e4365 authored by Herbert Xu's avatar Herbert Xu Committed by David S. Miller
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tun: Fix device unregister race 



It is currently possible for an asynchronous device unregister
to cause the same tun device to be unregistered twice.  This
is because the unregister in tun_chr_close only checks whether
__tun_get(tfile) != NULL.  This however has nothing to do with
whether the device has already been unregistered.  All it tells
you is whether __tun_detach has been called.

This patch fixes this by using the most obvious thing to test
whether the device has been unregistered.

It also moves __tun_detach outside of rtnl_unlock since nothing
that it does requires that lock.

Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c001c213

drivers/net/tun.c

+9 −7
Original line number Diff line number Diff line
@@ -1324,20 +1324,22 @@ static int tun_chr_close(struct inode *inode, struct file *file) 
	struct tun_file *tfile = file->private_data;

	struct tun_struct *tun;





	rtnl_lock();

	tun = __tun_get(tfile);

	if (tun) {

		DBG(KERN_INFO "%s: tun_chr_close\n", tun->dev->name);

		struct net_device *dev = tun->dev;



		DBG(KERN_INFO "%s: tun_chr_close\n", dev->name);



		__tun_detach(tun);



		/* If desireable, unregister the netdevice. */

		if (!(tun->flags & TUN_PERSIST))

			unregister_netdevice(tun->dev);



	}

		if (!(tun->flags & TUN_PERSIST)) {

			rtnl_lock();

			if (dev->reg_state == NETREG_REGISTERED)

				unregister_netdevice(dev);

			rtnl_unlock();

		}

	}



	tun = tfile->tun;

	if (tun)