can: j1939: socket: j1939_sk_bind(): make sure ml_priv is allocated

This patch adds check to ensure that the struct net_device::ml_priv is
allocated, as it is used later by the j1939 stack.

The allocation is done by all mainline CAN network drivers, but when using
bond or team devices this is not the case.

Bail out if no ml_priv is allocated.

Reported-by: syzbot+f03d384f3455d28833eb@syzkaller.appspotmail.com
Fixes: 9d71dd0c ("can: add support of SAE J1939 protocol")
Cc: linux-stable <stable@vger.kernel.org> # >= v5.4
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://lore.kernel.org/r/20200807105200.26441-4-o.rempel@pengutronix.deSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

net/can/j1939/socket.c

@@ -467,6 +467,14 @@ static int j1939_sk_bind(struct socket *sock, struct sockaddr *uaddr, int len)
 			goto out_release_sock;
 		}
 
+		if (!ndev->ml_priv) {
+			netdev_warn_once(ndev,
+					 "No CAN mid layer private allocated, please fix your driver and use alloc_candev()!\n");
+			dev_put(ndev);
+			ret = -ENODEV;
+			goto out_release_sock;
+		}
+
 		priv = j1939_netdev_start(ndev);
 		dev_put(ndev);
 		if (IS_ERR(priv)) {