[PATCH] team: reject ARPHRD_CAN devices in team_port_add

[Jiale Yao <yaojiale02@163.com>]

Enslaving a CAN device (e.g. vxcan) to a team master triggers a
NULL pointer dereference in can_rx_unregister() inside
net/can/af_can.c.

During team_port_add(), the code only checks IFF_LOOPBACK but
does not reject ARPHRD_CAN devices.  After passing this gate,
team_dev_type_check_change() calls team_setup_by_port() which
sets dev->type = port_dev->type, adopting the CAN type for the
team device.  However, CAN devices operate on a fundamentally
different Layer 2 architecture, relying on the CAN mid-layer
private data structure (can_ml_priv) instead of standard
Ethernet structures.  Since the team driver never initializes
can_ml_priv, subsequent CAN subsystem operations -- such as
closing an ISOTP socket bound to the team interface via
isotp_release() -- reach can_rx_unregister() which dereferences
the NULL can_ml_priv, causing a kernel crash.

The bonding driver already rejects CAN devices since commit
8ba68464e478 ("bonding: refuse to enslave CAN devices").
Team, as a sibling aggregation path, needs the same protection.

Fix this by adding an explicit ARPHRD_CAN check in
team_port_add(), directly after the IFF_LOOPBACK guard,
consistent with the approach taken in bond_enslave().

Fixes: 1d76efe1577b ("team: add support for non-ethernet devices")
Assisted-by: Claude:deepseek-v4-pro
Signed-off-by: Jiale Yao <yaojiale02@163.com>
---
 drivers/net/team/team_core.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/net/team/team_core.c b/drivers/net/team/team_core.c
index feaa75fbf8fc..38f88a836010 100644
--- a/drivers/net/team/team_core.c
+++ b/drivers/net/team/team_core.c
@@ -1224,6 +1224,13 @@ static int team_port_add(struct team *team, struct net_device *port_dev,
 		return -EINVAL;
 	}
 
+	if (port_dev->type == ARPHRD_CAN) {
+		NL_SET_ERR_MSG(extack, "CAN device can't be added as a team port");
+		netdev_err(dev, "Device %s is CAN device. CAN devices 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 "
-- 
2.34.1