[PATCH 4.14 21/42] batman-adv: Request iflink once in batadv_get_real_netdevice

Greg Kroah-Hartman
2022-03-07T09:26:44Z

From: Sven Eckelmann <sven@narfation.org>

commit 6116ba09423f7d140f0460be6a1644dceaad00da upstream.

There is no need to call dev_get_iflink multiple times for the same
net_device in batadv_get_real_netdevice. 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: 5ed4a460a1d3 ("batman-adv: additional checks for virtual interfaces on top of WiFi")
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 | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

--- a/net/batman-adv/hard-interface.c
+++ b/net/batman-adv/hard-interface.c
@@ -221,14 +221,16 @@ static struct net_device *batadv_get_rea
struct net_device *real_netdev = NULL;
struct net *real_net;
struct net *net;
- int ifindex;
+ int iflink;

ASSERT_RTNL();

if (!netdev)
return NULL;

- if (netdev->ifindex == dev_get_iflink(netdev)) {
+ iflink = dev_get_iflink(netdev);
+
+ if (netdev->ifindex == iflink) {
dev_hold(netdev);
return netdev;
}
@@ -238,9 +240,8 @@ static struct net_device *batadv_get_rea
goto out;

net = dev_net(hard_iface->soft_iface);
- ifindex = dev_get_iflink(netdev);
real_net = batadv_getlink_net(netdev, net);
- real_netdev = dev_get_by_index(real_net, ifindex);
+ real_netdev = dev_get_by_index(real_net, iflink);

out:
if (hard_iface)