batman-adv: Don't expect inter-netns unique iflink indices

The ifindex doesn't have to be unique for multiple network namespaces on
the same machine.

  $ ip netns add test1
  $ ip -net test1 link add dummy1 type dummy
  $ ip netns add test2
  $ ip -net test2 link add dummy2 type dummy

  $ ip -net test1 link show dev dummy1
  6: dummy1: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
      link/ether 96:81:55:1e:dd:85 brd ff:ff:ff:ff:ff:ff
  $ ip -net test2 link show dev dummy2
  6: dummy2: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
      link/ether 5a:3c:af:35:07:c3 brd ff:ff:ff:ff:ff:ff

But the batman-adv code to walk through the various layers of virtual
interfaces uses this assumption because dev_get_iflink handles it
internally and doesn't return the actual netns of the iflink. And
dev_get_iflink only documents the situation where ifindex == iflink for
physical devices.

But only checking for dev->netdev_ops->ndo_get_iflink is also not an option
because ipoib_get_iflink implements it even when it sometimes returns an
iflink != ifindex and sometimes iflink == ifindex. The caller must
therefore make sure itself to check both netns and iflink + ifindex for
equality. Only when they are equal, a "physical" interface was detected
which should stop the traversal. On the other hand, vxcan_get_iflink can
also return 0 in case there was currently no valid peer. In this case, it
is still necessary to stop.

Fixes: b7eddd0b3950 ("batman-adv: prevent using any virtual device created on batman-adv as hard-interface")
Fixes: 5ed4a460a1d3 ("batman-adv: additional checks for virtual interfaces on top of WiFi")
Reported-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>

diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c
index e2760cfce1909f2a2b4aec589759dbe4a82bdf7e..35fadb924849866f0fcdcd57ad136d158c398a93 100644 (file)
--- a/net/batman-adv/hard-interface.c
+++ b/net/batman-adv/hard-interface.c
@@ -157,13 +157,15 @@ static bool batadv_is_on_batman_iface(const struct net_device *net_dev)
                return true;
 
        iflink = dev_get_iflink(net_dev);
-
-       /* no more parents..stop recursion */
-       if (iflink == 0 || iflink == net_dev->ifindex)
+       if (iflink == 0)
                return false;
 
        parent_net = batadv_getlink_net(net_dev, net);
 
+       /* iflink to itself, most likely physical device */
+       if (net == parent_net && iflink == net_dev->ifindex)
+               return false;
+
        /* recurse over the parent device */
        parent_dev = __dev_get_by_index((struct net *)parent_net, iflink);
        /* if we got a NULL parent_dev there is something broken.. */
@@ -223,8 +225,7 @@ static struct net_device *batadv_get_real_netdevice(struct net_device *netdev)
                return NULL;
 
        iflink = dev_get_iflink(netdev);
-
-       if (netdev->ifindex == iflink) {
+       if (iflink == 0) {
                dev_hold(netdev);
                return netdev;
        }
@@ -235,6 +236,14 @@ static struct net_device *batadv_get_real_netdevice(struct net_device *netdev)
 
        net = dev_net(hard_iface->soft_iface);
        real_net = batadv_getlink_net(netdev, net);
+
+       /* iflink to itself, most likely physical device */
+       if (net == real_net && netdev->ifindex == iflink) {
+               real_netdev = netdev;
+               dev_hold(real_netdev);
+               goto out;
+       }
+
        real_netdev = dev_get_by_index(real_net, iflink);
 
 out: