can: isotp: isotp_release(): omit unintended hrtimer restart on socket release

When closing the isotp socket, the potentially running hrtimers are
canceled before removing the subscription for CAN identifiers via
can_rx_unregister().

This may lead to an unintended (re)start of a hrtimer in
isotp_rcv_cf() and isotp_rcv_fc() in the case that a CAN frame is
received by isotp_rcv() while the subscription removal is processed.

However, isotp_rcv() is called under RCU protection, so after calling
can_rx_unregister, we may call synchronize_rcu in order to wait for
any RCU read-side critical sections to finish. This prevents the
reception of CAN frames after hrtimer_cancel() and therefore the
unintended (re)start of the hrtimers.

Link: https://lore.kernel.org/r/20210618173713.2296-1-socketcan@hartkopp.net
Fixes: e057dd3fc20f ("can: add ISO 15765-2:2016 transport protocol")
Cc: linux-stable <stable@vger.kernel.org>
Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/net/can/isotp.c b/net/can/isotp.c
index be6183f..234cc4a 100644 (file)
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -1028,9 +1028,6 @@ static int isotp_release(struct socket *sock)
 
        lock_sock(sk);
 
-       hrtimer_cancel(&so->txtimer);
-       hrtimer_cancel(&so->rxtimer);
-
        /* remove current filters & unregister */
        if (so->bound && (!(so->opt.flags & CAN_ISOTP_SF_BROADCAST))) {
                if (so->ifindex) {
@@ -1042,10 +1039,14 @@ static int isotp_release(struct socket *sock)
                                                  SINGLE_MASK(so->rxid),
                                                  isotp_rcv, sk);
                                dev_put(dev);
+                               synchronize_rcu();
                        }
                }
        }
 
+       hrtimer_cancel(&so->txtimer);
+       hrtimer_cancel(&so->rxtimer);
+
        so->ifindex = 0;
        so->bound = 0;