[PATCH net v2 1/3] can: dev: prevent bus-off recovery when the interface is not running

[Cunhao Lu]

The networking core clears __LINK_STATE_START before calling ndo_stop(),
but CAN bus-off recovery neither checks this state before queuing work
nor before calling the driver's restart callback. Recovery can therefore
be queued or started after the interface has begun closing, potentially
re-enabling hardware while the driver is tearing it down.

Check netif_running() in can_restart() before flushing echo skbs, sending
the restart notification or enabling the carrier. Keep the existing
unsupported-operation check first. In can_bus_off(), only schedule
recovery for a running interface and make the log message reflect that
decision. Keep reporting bus-off and disabling the carrier.

These checks do not wait for recovery that has already passed the check,
nor serialize the check with work submission. Drivers still need to
cancel restart work before tearing down resources and quiesce its
producers before their final cleanup.

Fixes: 39549eef3587 ("can: CAN Network device driver and Netlink interface")
Cc: stable at vger.kernel.org
Signed-off-by: Cunhao Lu <1579567540 at qq.com>
---
 drivers/net/can/dev/dev.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/can/dev/dev.c b/drivers/net/can/dev/dev.c
index 769745e22a3c7..92492c503446e 100644
--- a/drivers/net/can/dev/dev.c
+++ b/drivers/net/can/dev/dev.c
@@ -198,6 +198,9 @@ static int can_restart(struct net_device *dev)
 	if (!priv->do_set_mode)
 		return -EOPNOTSUPP;
 
+	if (!netif_running(dev))
+		return -ENETDOWN;
+
 	if (netif_carrier_ok(dev))
 		netdev_err(dev, "Attempt to restart for bus-off recovery, but carrier is OK?\n");
 
@@ -264,8 +267,9 @@ int can_restart_now(struct net_device *dev)
 void can_bus_off(struct net_device *dev)
 {
 	struct can_priv *priv = netdev_priv(dev);
+	const bool restart = priv->restart_ms && netif_running(dev);
 
-	if (priv->restart_ms)
+	if (restart)
 		netdev_info(dev, "bus-off, scheduling restart in %d ms\n",
 			    priv->restart_ms);
 	else
@@ -273,7 +277,7 @@ void can_bus_off(struct net_device *dev)
 
 	netif_carrier_off(dev);
 
-	if (priv->restart_ms)
+	if (restart)
 		schedule_delayed_work(&priv->restart_work,
 				      msecs_to_jiffies(priv->restart_ms));
 }

-- 
2.34.1