[maint,2/3] batman-adv: Request iflink once in batadv_get_real_netdevice

Message ID 20220302184946.414934-2-sven@narfation.org (mailing list archive)
State Accepted, archived
Delegated to: Simon Wunderlich
Series [maint,1/3] batman-adv: Request iflink once in batadv-on-batadv check |

Commit Message

Sven Eckelmann March 2, 2022, 6:49 p.m. UTC
  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: 2b45bb6c3aad ("batman-adv: additional checks for virtual interfaces on top of WiFi")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
 net/batman-adv/hard-interface.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)


diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c
index 774a26c5..8ed128bb 100644
--- a/net/batman-adv/hard-interface.c
+++ b/net/batman-adv/hard-interface.c
@@ -215,14 +215,16 @@  static struct net_device *batadv_get_real_netdevice(struct net_device *netdev)
 	struct net_device *real_netdev = NULL;
 	struct net *real_net;
 	struct net *net;
-	int ifindex;
+	int iflink;
 	if (!netdev)
 		return NULL;
-	if (netdev->ifindex == dev_get_iflink(netdev)) {
+	iflink = dev_get_iflink(netdev);
+	if (netdev->ifindex == iflink) {
 		return netdev;
@@ -232,9 +234,8 @@  static struct net_device *batadv_get_real_netdevice(struct net_device *netdev)
 		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);