[1/3] batman-adv: Request iflink once in batadv-on-batadv check

Commit Message

Simon Wunderlich March 2, 2022, 4:30 p.m. UTC

From: Sven Eckelmann <[e-mail]>

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: b7eddd0b3950 ("batman-adv: prevent using any virtual device created on batman-adv as hard-interface")
Signed-off-by: Sven Eckelmann <[e-mail]>
Signed-off-by: Simon Wunderlich <[e-mail]>
---
 net/batman-adv/hard-interface.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

Comments

[e-mail] March 3, 2022, 6 a.m. UTC | #1

Hello:

This series was applied to netdev/net.git (master)
by Simon Wunderlich <[e-mail]>:

On Wed,  2 Mar 2022 17:30:47 +0100 you wrote:
> From: Sven Eckelmann <[e-mail]>
> 
> 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.
> 
> [...]

Here is the summary with links:
  - [1/3] batman-adv: Request iflink once in batadv-on-batadv check
    https://git.kernel.org/netdev/net/c/690bb6fb64f5
  - [2/3] batman-adv: Request iflink once in batadv_get_real_netdevice
    https://git.kernel.org/netdev/net/c/6116ba09423f
  - [3/3] batman-adv: Don't expect inter-netns unique iflink indices
    https://git.kernel.org/netdev/net/c/6c1f41afc1db

You are awesome, thank you!

Patch

diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c
index 8a2b78f9c4b2..35aa1122043b 100644
--- a/net/batman-adv/hard-interface.c
+++ b/net/batman-adv/hard-interface.c
@@ -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");