[lvc-project] [PATCH v3 2/2] can: j1939: cancel all pending ECUs on device stop

[Dmitry Antipov]

Cancel all pending ECUs in j1939_netdev_stop(). This is needed
to prevent the case when stopped device no longer processes ECUs
and, since ECU holds the reference to 'struct j1939_priv', the
latter (and ECU itself) is never freed.

Reported-by: syzbot+489e907b2a026a6f5fa0 at syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=489e907b2a026a6f5fa0
Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol")
Signed-off-by: Dmitry Antipov <dmantipov at yandex.ru>
---
v3: rebase on top of lockless hrtimer handler
    and asynchronous ECU freeing
v2: add extra precaution to avoid ABBA deadlock between
    j1939_ecu_cancel_all() and timer callbacks (Sashiko)
---
 net/can/j1939/bus.c        | 10 ++++++++++
 net/can/j1939/j1939-priv.h |  1 +
 net/can/j1939/main.c       |  1 +
 3 files changed, 12 insertions(+)

diff --git a/net/can/j1939/bus.c b/net/can/j1939/bus.c
index a347594b8c1c..b021a77a0898 100644
--- a/net/can/j1939/bus.c
+++ b/net/can/j1939/bus.c
@@ -132,6 +132,16 @@ void j1939_ecu_timer_cancel(struct j1939_ecu *ecu)
 		j1939_ecu_put(ecu);
 }
 
+void j1939_ecu_cancel_all(struct j1939_priv *priv)
+{
+	struct j1939_ecu *ecu, *tmp;
+
+	write_lock_bh(&priv->lock);
+	list_for_each_entry_safe(ecu, tmp, &priv->ecus, list)
+		j1939_ecu_timer_cancel(ecu);
+	write_unlock_bh(&priv->lock);
+}
+
 static enum hrtimer_restart j1939_ecu_timer_handler(struct hrtimer *hrtimer)
 {
 	struct j1939_ecu *ecu =
diff --git a/net/can/j1939/j1939-priv.h b/net/can/j1939/j1939-priv.h
index 080d5b4c8c23..311d89f9b473 100644
--- a/net/can/j1939/j1939-priv.h
+++ b/net/can/j1939/j1939-priv.h
@@ -205,6 +205,7 @@ struct j1939_ecu *j1939_ecu_create_locked(struct j1939_priv *priv, name_t name);
 
 void j1939_ecu_timer_start(struct j1939_ecu *ecu);
 void j1939_ecu_timer_cancel(struct j1939_ecu *ecu);
+void j1939_ecu_cancel_all(struct j1939_priv *priv);
 void j1939_ecu_unmap_all(struct j1939_priv *priv);
 
 struct j1939_priv *j1939_netdev_start(struct net_device *ndev);
diff --git a/net/can/j1939/main.c b/net/can/j1939/main.c
index 5e5e6c228f22..1f68ba803700 100644
--- a/net/can/j1939/main.c
+++ b/net/can/j1939/main.c
@@ -306,6 +306,7 @@ struct j1939_priv *j1939_netdev_start(struct net_device *ndev)
 
 void j1939_netdev_stop(struct j1939_priv *priv)
 {
+	j1939_ecu_cancel_all(priv);
 	kref_put_mutex(&priv->rx_kref, __j1939_rx_release, &j1939_netdev_lock);
 	j1939_priv_put(priv);
 }
-- 
2.55.0