Commit 1809c82a authored Jan 14, 2026 by Tetsuo Handa Committed by Marc Kleine-Budde Jan 15, 2026

net: can: j1939: j1939_xtp_rx_rts_session_active(): deactivate session upon...


net: can: j1939: j1939_xtp_rx_rts_session_active(): deactivate session upon receiving the second rts

Since j1939_session_deactivate_activate_next() in j1939_tp_rxtimer() is
called only when the timer is enabled, we need to call
j1939_session_deactivate_activate_next() if we cancelled the timer.
Otherwise, refcount for j1939_session leaks, which will later appear as

| unregister_netdevice: waiting for vcan0 to become free. Usage count = 2.

problem.

Reported-by: syzbot <syzbot+881d65229ca4f9ae8c84@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=881d65229ca4f9ae8c84


Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Tested-by: Oleksij Rempel <o.rempel@pengutronix.de>
Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>
Fixes: 9d71dd0c ("can: add support of SAE J1939 protocol")
Link: https://patch.msgid.link/b1212653-8fa1-44e1-be9d-12f950fb3a07@I-love.SAKURA.ne.jp


Cc: stable@vger.kernel.org
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

parent 6c1f5146

net/can/j1939/transport.c

+9 −1

Original line number	Diff line number	Diff line
		@@ -1695,8 +1695,16 @@ static int j1939_xtp_rx_rts_session_active(struct j1939_session *session,

		j1939_session_timers_cancel(session);
		j1939_session_cancel(session, J1939_XTP_ABORT_BUSY);
		if (session->transmission)
		if (session->transmission) {
		j1939_session_deactivate_activate_next(session);
		} else if (session->state == J1939_SESSION_WAITING_ABORT) {
		/* Force deactivation for the receiver.
		* If we rely on the timer starting in j1939_session_cancel,
		* a second RTS call here will cancel that timer and fail
		* to restart it because the state is already WAITING_ABORT.
		*/
		j1939_session_deactivate_activate_next(session);
		}

		return -EBUSY;
		}