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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: b7eddd0b39 ("batman-adv: prevent using any virtual device created on batman-adv as hard-interface")
Fixes: 5ed4a460a1 ("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>
This commit is contained in:
Sven Eckelmann 2022-02-27 23:23:49 +01:00 committed by Simon Wunderlich
parent 6116ba0942
commit 6c1f41afc1
1 changed files with 14 additions and 5 deletions
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19
net/batman-adv/hard-interface.c
View File

@ -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: