[PATCH bpf-next v2] net: Don't allow to attach xdp if bond slave device's upper already has a program

[Feng zhou <zhoufeng.zf@bytedance.com>]

From: Feng Zhou <zhoufeng.zf@bytedance.com>

Cannot attach when an upper device already has a program, This
restriction is only for bond's slave devices or team port, and
should not be accidentally injured for devices like eth0 and vxlan0.

Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Feng Zhou <zhoufeng.zf@bytedance.com>
---
Changelog:
v1->v2: Addressed comments from Paolo Abeni, Jiri Pirko
- Use "netif_is_lag_port" relace of "netif_is_bond_slave"
Details in here:
https://lore.kernel.org/netdev/3bf84d23-a561-47ae-84a4-e99488fc762b@bytedance.com/T/

 net/core/dev.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index f66e61407883..49144e62172e 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -9502,10 +9502,12 @@ static int dev_xdp_attach(struct net_device *dev, struct netlink_ext_ack *extack
 	}
 
 	/* don't allow if an upper device already has a program */
-	netdev_for_each_upper_dev_rcu(dev, upper, iter) {
-		if (dev_xdp_prog_count(upper) > 0) {
-			NL_SET_ERR_MSG(extack, "Cannot attach when an upper device already has a program");
-			return -EEXIST;
+	if (netif_is_lag_port(dev)) {
+		netdev_for_each_upper_dev_rcu(dev, upper, iter) {
+			if (dev_xdp_prog_count(upper) > 0) {
+				NL_SET_ERR_MSG(extack, "Cannot attach when an upper device already has a program");
+				return -EEXIST;
+			}
 		}
 	}
 
-- 
2.30.2