| From | Greg Kroah-Hartman <> | Subject | [PATCH 5.10 048/105] batman-adv: Dont expect inter-netns unique iflink indices | Date | Mon, 7 Mar 2022 10:18:51 +0100 |
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From: Sven Eckelmann <sven@narfation.org>
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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- net/batman-adv/hard-interface.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-)
--- 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(co 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_rea 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_rea 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:
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