The following commit has been merged in the batadv/lts/5.4 branch: commit 2d268481148c6e5487b67fbdcdc3834aad397ff6 Author: Sven Eckelmann sven@narfation.org Date: Sun Feb 27 23:23:49 2022 +0100

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: 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 d896208775db..5f44c94ad707 100644 --- a/net/batman-adv/hard-interface.c +++ b/net/batman-adv/hard-interface.c @@ -159,13 +159,15 @@ 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.. */ @@ -225,8 +227,7 @@ 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; } @@ -237,6 +238,14 @@ 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: