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batman-adv: Request iflink once in batadv-on-batadv check
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commit 690bb6f upstream.

There is no need to call dev_get_iflink multiple times for the same
net_device in batadv_is_on_batman_iface. And since some of the
.ndo_get_iflink callbacks are dynamic (for example via RCUs like in
vxcan_get_iflink), it could easily happen that the returned values are not
stable. The pre-checks before __dev_get_by_index are then of course bogus.

Fixes: b7eddd0 ("batman-adv: prevent using any virtual device created on batman-adv as hard-interface")
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>
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ecsv authored and gregkh committed Mar 8, 2022
1 parent c7ea6e6 commit fb6812a
Showing 1 changed file with 5 additions and 4 deletions.
9 changes: 5 additions & 4 deletions net/batman-adv/hard-interface.c
Expand Up @@ -149,22 +149,23 @@ static bool batadv_is_on_batman_iface(const struct net_device *net_dev)
struct net *net = dev_net(net_dev);
struct net_device *parent_dev;
struct net *parent_net;
int iflink;
bool ret;

/* check if this is a batman-adv mesh interface */
if (batadv_softif_is_valid(net_dev))
return true;

iflink = dev_get_iflink(net_dev);

/* no more parents..stop recursion */
if (dev_get_iflink(net_dev) == 0 ||
dev_get_iflink(net_dev) == net_dev->ifindex)
if (iflink == 0 || iflink == net_dev->ifindex)
return false;

parent_net = batadv_getlink_net(net_dev, net);

/* recurse over the parent device */
parent_dev = __dev_get_by_index((struct net *)parent_net,
dev_get_iflink(net_dev));
parent_dev = __dev_get_by_index((struct net *)parent_net, iflink);
/* if we got a NULL parent_dev there is something broken.. */
if (!parent_dev) {
pr_err("Cannot find parent device\n");
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