[PATCH net v5] team: reject CAN, IEEE 802.15.4 and 6LoWPAN devices in team_port_add

From: Jiale Yao <redacted>

When the first port has a non-Ethernet type, team_setup_by_port()
copies port_dev->type to the team device while netdev_priv() of the
team device still holds a struct team. Several L2 stacks identify their
devices by dev->type alone and then access type specific data that the
team driver never sets up:

- CAN protocols rely on the CAN mid-layer private data (ml_priv)
- IEEE 802.15.4 code dereferences ieee802154_ptr and the mlme ops in
  ml_priv
- the 6LoWPAN netdev notifier writes through lowpan_dev(dev) on
  NETDEV_DOWN and reads it on NETDEV_UP/NETDEV_CHANGE

Enslaving such a device (e.g. vxcan, wpan0, lowpan0) therefore leads to
NULL pointer dereferences or to writes into struct team.

This is the same problem that syzbot reported for the bonding driver
with a vxcan device enslaved to a bond master, which crashed in
can_rx_unregister() and was fixed by commit 8ba68464e478 ("bonding:
refuse to enslave CAN devices"). The team driver has the same gap.

Reject ARPHRD_CAN, ARPHRD_IEEE802154, ARPHRD_IEEE802154_MONITOR and
ARPHRD_6LOWPAN devices in team_port_add().

Link: https://lore.kernel.org/all/b58d98e0-8fe3-4e4e-b8a5-c1c7e647ccca@hartkopp.net/ (local)
Link: https://syzkaller.appspot.com/bug?extid=8ed98cbd0161632bce95 # bonding splat
Fixes: 1d76efe1577b ("team: add support for non-ethernet devices")
Assisted-by: Claude:deepseek-v4-pro
Signed-off-by: Jiale Yao <redacted>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
---
v5: [Hartkopp] reference the syzbot report of the identical bonding problem
v4: [Hartkopp] also reject ARPHRD_6LOWPAN as reported by Sashiko AI
    review, reworded commit message (bonding only rejects CAN)
v3: [Hartkopp] fixed indention and compilation as reported by kernel test robot
---
 drivers/net/team/team_core.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/net/team/team_core.c b/drivers/net/team/team_core.c
--- a/drivers/net/team/team_core.c
+++ b/drivers/net/team/team_core.c

@@ -1223,10 +1223,21 @@ static int team_port_add(struct team *team, struct net_device *port_dev,
 		netdev_err(dev, "Device %s is loopback device. Loopback devices can't be added as a team port\n",
 			   portname);
 		return -EINVAL;
 	}

+	if (port_dev->type == ARPHRD_CAN ||
+	    port_dev->type == ARPHRD_IEEE802154 ||
+	    port_dev->type == ARPHRD_IEEE802154_MONITOR ||
+	    port_dev->type == ARPHRD_6LOWPAN) {
+		NL_SET_ERR_MSG(extack,
+			       "CAN, IEEE 802.15.4 and 6LoWPAN devices can't be added as a team port");
+		netdev_err(dev, "Device %s is CAN, IEEE 802.15.4 or 6LoWPAN. These device types can't be added as a team port\n",
+			   portname);
+		return -EINVAL;
+	}
+
 	if (netif_is_team_port(port_dev)) {
 		NL_SET_ERR_MSG(extack, "Device is already a port of a team device");
 		netdev_err(dev, "Device %s is already a port "
 				"of a team device\n", portname);
 		return -EBUSY;
--

2.53.0