can: isotp: check CAN address family in isotp_bind()

Add missing check to block non-AF_CAN binds.

Syzbot created some code which matched the right sockaddr struct size but used AF_XDP (0x2C) instead of AF_CAN (0x1D) in the address family field:

bind$xdp(r2, &(0x7f0000000540)={0x2c, 0x0, r4, 0x0, r2}, 0x10)

                                ^^^^

This has no funtional impact but the userspace should be notified about the wrong address family field content.

---
 net/can/isotp.c | 3 +++
 1 file changed, 3 insertions(+)

index fc81d77724a1..9bc344851704 100644
@@ -1218,10 +1218,13 @@ static int isotp_bind(struct socket *sock, struct sockaddr *uaddr, int len)
 	int notify_enetdown = 0;
 
 	if (len < ISOTP_MIN_NAMELEN)
 		return -EINVAL;
 
+	if (addr->can_family != AF_CAN)
+		return -EINVAL;
+
 	/* sanitize tx CAN identifier */
 	if (tx_id & CAN_EFF_FLAG)
 		tx_id &= (CAN_EFF_FLAG | CAN_EFF_MASK);
 	else
 		tx_id &= CAN_SFF_MASK;

2.35.1