[PATCH net-next] net: dsa: sja1105: flower: reject cross-chip redirect

[David Yang <mmyangfl@gmail.com>]

The driver silently accepts a destination port on a different switch
chip, then programs its index (on another chip) into the local hardware,
which redirects to the wrong port or possibly crashes if the port index
is out of bound locally.

Add a check for it and adjust the extack message.

Signed-off-by: David Yang <mmyangfl@gmail.com>
---
 drivers/net/dsa/sja1105/sja1105_flower.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/dsa/sja1105/sja1105_flower.c b/drivers/net/dsa/sja1105/sja1105_flower.c
index fba926f85b47..7547999a113f 100644
--- a/drivers/net/dsa/sja1105/sja1105_flower.c
+++ b/drivers/net/dsa/sja1105/sja1105_flower.c
@@ -391,9 +391,9 @@ int sja1105_cls_flower_add(struct dsa_switch *ds, int port,
 			struct dsa_port *to_dp;
 
 			to_dp = dsa_port_from_netdev(act->dev);
-			if (IS_ERR(to_dp)) {
+			if (IS_ERR(to_dp) || to_dp->ds != ds) {
 				NL_SET_ERR_MSG_MOD(extack,
-						   "Destination not a switch port");
+						   "Destination not a local switch port");
 				return -EOPNOTSUPP;
 			}
 
-- 
2.53.0