Commit 92a556ef authored Feb 27, 2022 by Sven Eckelmann Committed by Greg Kroah-Hartman Mar 08, 2022

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



commit 6c1f41afc1dbe59d9d3c8bb0d80b749c119aa334 upstream.

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: b7eddd0b ("batman-adv: prevent using any virtual device created on batman-adv as hard-interface")
Fixes: 5ed4a460 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 130ec90c

net/batman-adv/hard-interface.c

+14 −5

Original line number	Diff line number	Diff line
		@@ -170,13 +170,15 @@ 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.. */
		@@ -236,8 +238,7 @@ 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;
		}
		@@ -248,6 +249,14 @@ 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: