can: isotp: isotp_bind(): do not validate unused address information

JIRA: https://issues.redhat.com/browse/RHEL-80832

commit b76b163
Author: Oliver Hartkopp <socketcan@hartkopp.net>
Date:   Tue May 17 16:56:53 2022 +0200

    can: isotp: isotp_bind(): do not validate unused address information

    With commit 2aa3988 ("can: isotp: isotp_bind(): return -EINVAL on
    incorrect CAN ID formatting") the bind() syscall returns -EINVAL when
    the given CAN ID needed to be sanitized. But in the case of an unconfirmed
    broadcast mode the rx CAN ID is not needed and may be uninitialized from
    the caller - which is ok.

    This patch makes sure the result of an inproper CAN ID format is only
    provided when the address information is needed.

    Link: https://lore.kernel.org/all/20220517145653.2556-1-socketcan@hartkopp.net
    Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
    Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

Signed-off-by: Radu Rendec <rrendec@redhat.com>

Author: rrendec

net/can/isotp.c

@@ -1202,31 +1202,36 @@ static int isotp_bind(struct socket *sock, struct sockaddr *uaddr, int len)
 	struct net *net = sock_net(sk);
 	int ifindex;
 	struct net_device *dev;
-	canid_t tx_id, rx_id;
+	canid_t tx_id = addr->can_addr.tp.tx_id;
+	canid_t rx_id = addr->can_addr.tp.rx_id;
 	int err = 0;
 	int notify_enetdown = 0;
 
 	if (len < ISOTP_MIN_NAMELEN)
 		return -EINVAL;
 
-	/* sanitize tx/rx CAN identifiers */
-	tx_id = addr->can_addr.tp.tx_id;
+	/* sanitize tx CAN identifier */
 	if (tx_id & CAN_EFF_FLAG)
 		tx_id &= (CAN_EFF_FLAG | CAN_EFF_MASK);
 	else
 		tx_id &= CAN_SFF_MASK;
 
-	rx_id = addr->can_addr.tp.rx_id;
-	if (rx_id & CAN_EFF_FLAG)
-		rx_id &= (CAN_EFF_FLAG | CAN_EFF_MASK);
-	else
-		rx_id &= CAN_SFF_MASK;
-
-	/* give feedback on wrong CAN-ID values */
-	if (tx_id != addr->can_addr.tp.tx_id ||
-	    rx_id != addr->can_addr.tp.rx_id)
+	/* give feedback on wrong CAN-ID value */
+	if (tx_id != addr->can_addr.tp.tx_id)
 		return -EINVAL;
 
+	/* sanitize rx CAN identifier (if needed) */
+	if (isotp_register_rxid(so)) {
+		if (rx_id & CAN_EFF_FLAG)
+			rx_id &= (CAN_EFF_FLAG | CAN_EFF_MASK);
+		else
+			rx_id &= CAN_SFF_MASK;
+
+		/* give feedback on wrong CAN-ID value */
+		if (rx_id != addr->can_addr.tp.rx_id)
+			return -EINVAL;
+	}
+
 	if (!addr->can_ifindex)
 		return -ENODEV;