When the a large chunk of data send and the receiver does not send a Flow Control frame back in time, the sendmsg() does not return a error code, but the number of bytes sent corresponding to the size of the packet.

If a timeout occurs the isotp_tx_timer_handler() is fired, sets sk->sk_err and calls the sk->sk_error_report() function. It was wrongly expected that the error would be propagated to user space in every case. For isotp_sendmsg() blocking on wait_event_interruptible() this is not the case.

This patch fixes the problem by checking if sk->sk_err is set and returning the error to user space.

Fixes: e057dd3fc20f ("can: add ISO 15765-2:2016 transport protocol") Link: https://github.com/hartkopp/can-isotp/issues/42 Link: https://github.com/hartkopp/can-isotp/pull/43 Link: https://lore.kernel.org/all/20210507091839.1366379-1-mkl@pengutronix.de Cc: stable@vger.kernel.org Reported-by: Sottas Guillaume (LMB) Guillaume.Sottas@liebherr.com Tested-by: Oliver Hartkopp socketcan@hartkopp.net Signed-off-by: Marc Kleine-Budde mkl@pengutronix.de --- net/can/isotp.c | 3 +++ 1 file changed, 3 insertions(+)

diff --git a/net/can/isotp.c b/net/can/isotp.c index d1f54273c0bb..df6968b28bf4 100644 --- a/net/can/isotp.c +++ b/net/can/isotp.c @@ -971,6 +971,9 @@ static int isotp_sendmsg(struct socket *sock, struct msghdr *msg, size_t size) if (wait_tx_done) { /* wait for complete transmission of current pdu */ wait_event_interruptible(so->wait, so->tx.state == ISOTP_IDLE); + + if (sk->sk_err) + return -sk->sk_err; }

return size;

base-commit: 8a64ef042eab8a6cec04a6c79d44d1af79b628ca