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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: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Herbert Xu 2009-07-02 23:03:55 +00:00 committed by David S. Miller
parent c001c213b1
commit d23e43658a
1 changed files with 9 additions and 7 deletions
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16
drivers/net/tun.c
View File

@ -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();
}
}
rtnl_unlock();
tun = tfile->tun;
if (tun)