Commit 42bf50a1 authored by Oliver Hartkopp's avatar Oliver Hartkopp Committed by Marc Kleine-Budde
Browse files

can: isotp: support MSG_TRUNC flag when reading from socket 

When providing the MSG_TRUNC flag via recvmsg() syscall the return value
provides the real length of the packet or datagram, even when it was longer
than the passed buffer.

Fixes: e057dd3f ("can: add ISO 15765-2:2016 transport protocol")
Link: https://github.com/linux-can/can-utils/issues/347#issuecomment-1065932671
Link: https://lore.kernel.org/all/20220316164258.54155-3-socketcan@hartkopp.net


Suggested-by: default avatarDerek Will <derekrobertwill@gmail.com>
Signed-off-by: default avatarOliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: default avatarMarc Kleine-Budde <mkl@pengutronix.de>
parent 30ffd533

net/can/isotp.c

+15 −12
Original line number Diff line number Diff line
@@ -1047,29 +1047,28 @@ static int isotp_recvmsg(struct socket *sock, struct msghdr *msg, size_t size, 
	struct sock *sk = sock->sk;

	struct sk_buff *skb;

	struct isotp_sock *so = isotp_sk(sk);

	int err = 0;

	int noblock;

	int noblock = flags & MSG_DONTWAIT;

	int ret = 0;



	noblock = flags & MSG_DONTWAIT;

	flags &= ~MSG_DONTWAIT;

	if (flags & ~(MSG_DONTWAIT | MSG_TRUNC))

		return -EINVAL;



	if (!so->bound)

		return -EADDRNOTAVAIL;



	skb = skb_recv_datagram(sk, flags, noblock, &err);

	flags &= ~MSG_DONTWAIT;

	skb = skb_recv_datagram(sk, flags, noblock, &ret);

	if (!skb)

		return err;

		return ret;



	if (size < skb->len)

		msg->msg_flags |= MSG_TRUNC;

	else

		size = skb->len;



	err = memcpy_to_msg(msg, skb->data, size);

	if (err < 0) {

		skb_free_datagram(sk, skb);

		return err;

	}

	ret = memcpy_to_msg(msg, skb->data, size);

	if (ret < 0)

		goto out_err;



	sock_recv_timestamp(msg, sk, skb);
@@ -1079,9 +1078,13 @@ static int isotp_recvmsg(struct socket *sock, struct msghdr *msg, size_t size, 
		memcpy(msg->msg_name, skb->cb, msg->msg_namelen);

	}



	/* set length of return value */

	ret = (flags & MSG_TRUNC) ? skb->len : size;



out_err:

	skb_free_datagram(sk, skb);



	return size;

	return ret;

}



static int isotp_release(struct socket *sock)