From: Tetsuo Handa 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 Closes: https://syzkaller.appspot.com/bug?extid=881d65229ca4f9ae8c84 Signed-off-by: Tetsuo Handa Tested-by: Oleksij Rempel Acked-by: Oleksij Rempel Fixes: 9d71dd0c7009 ("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 --- net/can/j1939/transport.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c index 613a911dda10..8656ab388c83 100644 --- a/net/can/j1939/transport.c +++ b/net/can/j1939/transport.c @@ -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; } -- 2.51.0