From: Ben Hutchings <ben@decadent.org.uk>

This applies to 2.6.32 *only*.  It has not been applied upstream since
the limitation no longer exists.

Prior to Linux 2.6.35, net devices outside the initial net namespace
did not have sysfs directories.  Attempting to add attributes to
them will trigger a BUG().

Reported-and-tested-by: Russell Stuart <russell-debian@stuart.id.au>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 drivers/net/tun.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1006,7 +1006,8 @@ static int tun_set_iff(struct net *net,
 		if (err < 0)
 			goto err_free_sk;
 
-		if (device_create_file(&tun->dev->dev, &dev_attr_tun_flags) ||
+		if (!net_eq(dev_net(tun->dev), &init_net) ||
+		    device_create_file(&tun->dev->dev, &dev_attr_tun_flags) ||
 		    device_create_file(&tun->dev->dev, &dev_attr_owner) ||
 		    device_create_file(&tun->dev->dev, &dev_attr_group))
 			printk(KERN_ERR "Failed to create tun sysfs files\n");