can: introduce CAN_REQUIRED_SIZE macro

The size of this structure will be increased with J1939 support. To stay
binary compatible, the CAN_REQUIRED_SIZE macro is introduced for
existing CAN protocols.
Signed-off-by: Kurt Van Dijck <dev.kurt@vandijck-laurijssen.be>
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

include/linux/can/core.h

@@ -41,6 +41,14 @@ struct can_proto {
 	struct proto *prot;
 };
 
+/* required_size
+ * macro to find the minimum size of a struct
+ * that includes a requested member
+ */
+#define CAN_REQUIRED_SIZE(struct_type, member) \
+	(offsetof(typeof(struct_type), member) + \
+	 sizeof(((typeof(struct_type) *)(NULL))->member))
+
 /* function prototypes for the CAN networklayer core (af_can.c) */
 
 extern int  can_proto_register(const struct can_proto *cp);

net/can/bcm.c

@@ -1294,7 +1294,7 @@ static int bcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
 		/* no bound device as default => check msg_name */
 		DECLARE_SOCKADDR(struct sockaddr_can *, addr, msg->msg_name);
 
-		if (msg->msg_namelen < sizeof(*addr))
+		if (msg->msg_namelen < CAN_REQUIRED_SIZE(*addr, can_ifindex))
 			return -EINVAL;
 
 		if (addr->can_family != AF_CAN)
@@ -1536,7 +1536,7 @@ static int bcm_connect(struct socket *sock, struct sockaddr *uaddr, int len,
 	struct net *net = sock_net(sk);
 	int ret = 0;
 
-	if (len < sizeof(*addr))
+	if (len < CAN_REQUIRED_SIZE(*addr, can_ifindex))
 		return -EINVAL;
 
 	lock_sock(sk);

net/can/raw.c

@@ -396,7 +396,7 @@ static int raw_bind(struct socket *sock, struct sockaddr *uaddr, int len)
 	int err = 0;
 	int notify_enetdown = 0;
 
-	if (len < sizeof(*addr))
+	if (len < CAN_REQUIRED_SIZE(*addr, can_ifindex))
 		return -EINVAL;
 	if (addr->can_family != AF_CAN)
 		return -EINVAL;
@@ -733,7 +733,7 @@ static int raw_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
 	if (msg->msg_name) {
 		DECLARE_SOCKADDR(struct sockaddr_can *, addr, msg->msg_name);
 
-		if (msg->msg_namelen < sizeof(*addr))
+		if (msg->msg_namelen < CAN_REQUIRED_SIZE(*addr, can_ifindex))
 			return -EINVAL;
 
 		if (addr->can_family != AF_CAN)