ip6_pol_route panic: Do not allow VLAN on loopback

Several tests in the ipv6 routing code check IFF_LOOPBACK, and
allowing stacking such as VLAN'ing on top of loopback results in a
netdevice which reports IFF_LOOPBACK but really isn't the loopback
device.

Instead of spamming the ipv6 routing code with even more special tests,
simply disallow VLAN over loopback.

The result of this patch is:

# modprobe 8021q
# vconfig add lo 43
ERROR: trying to add VLAN #43 to IF -:lo:-  error: Operation not supported

Signed-off-by: Krishna Kumar <krkumar2@in.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/net/loopback.c b/drivers/net/loopback.c
index ea0dc451da9c..d70fb76edb77 100644
--- a/drivers/net/loopback.c
+++ b/drivers/net/loopback.c
@@ -173,7 +173,8 @@ static void loopback_setup(struct net_device *dev)
                 | NETIF_F_RXCSUM
                 | NETIF_F_HIGHDMA
                 | NETIF_F_LLTX
-                | NETIF_F_NETNS_LOCAL;
+                | NETIF_F_NETNS_LOCAL
+                | NETIF_F_VLAN_CHALLENGED;
         dev->ethtool_ops        = &loopback_ethtool_ops;
         dev->header_ops         = &eth_header_ops;
         dev->netdev_ops         = &loopback_ops;