devlink: disallow reload operation during device cleanup

There is a race between driver code that does setup/cleanup of device
and devlink reload operation that in some drivers works with the same
code. Use after free could we easily obtained by running:

while true; do
        echo 10 > /sys/bus/netdevsim/new_device
        devlink dev reload netdevsim/netdevsim10 &
        echo 10 > /sys/bus/netdevsim/del_device
done

Fix this by enabling reload only after setup of device is complete and
disabling it at the beginning of the cleanup process.

Reported-by: Ido Schimmel <idosch@mellanox.com>
Fixes: 2d8dc5bbf4e7 ("devlink: Add support for reload")
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

5 files changed, 57 insertions, 4 deletions

diff --git a/drivers/net/ethernet/mellanox/mlx4/main.c b/drivers/net/ethernet/mellanox/mlx4/main.c
index 22c72fb7206a..77f056b0895e 100644
--- a/drivers/net/ethernet/mellanox/mlx4/main.c
+++ b/drivers/net/ethernet/mellanox/mlx4/main.c
@@ -4015,6 +4015,7 @@ static int mlx4_init_one(struct pci_dev *pdev, const struct pci_device_id *id)
 		goto err_params_unregister;
 
 	devlink_params_publish(devlink);
+	devlink_reload_enable(devlink);
 	pci_save_state(pdev);
 	return 0;
 
@@ -4126,6 +4127,8 @@ static void mlx4_remove_one(struct pci_dev *pdev)
 	struct devlink *devlink = priv_to_devlink(priv);
 	int active_vfs = 0;
 
+	devlink_reload_disable(devlink);
+
 	if (mlx4_is_slave(dev))
 		persist->interface_state |= MLX4_INTERFACE_STATE_NOWAIT;
 
diff --git a/drivers/net/ethernet/mellanox/mlxsw/core.c b/drivers/net/ethernet/mellanox/mlxsw/core.c
index e1a90f5bddd0..da436a6aad2f 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/core.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/core.c
@@ -1198,8 +1198,10 @@ __mlxsw_core_bus_device_register(const struct mlxsw_bus_info *mlxsw_bus_info,
 	if (err)
 		goto err_thermal_init;
 
-	if (mlxsw_driver->params_register)
+	if (mlxsw_driver->params_register) {
 		devlink_params_publish(devlink);
+		devlink_reload_enable(devlink);
+	}
 
 	return 0;
 
@@ -1263,6 +1265,8 @@ void mlxsw_core_bus_device_unregister(struct mlxsw_core *mlxsw_core,
 {
 	struct devlink *devlink = priv_to_devlink(mlxsw_core);
 
+	if (!reload)
+		devlink_reload_disable(devlink);
 	if (devlink_is_reload_failed(devlink)) {
 		if (!reload)
 			/* Only the parts that were not de-initialized in the
diff --git a/drivers/net/netdevsim/dev.c b/drivers/net/netdevsim/dev.c
index 3da96c7e8265..059711edfc61 100644
--- a/drivers/net/netdevsim/dev.c
+++ b/drivers/net/netdevsim/dev.c
@@ -820,6 +820,7 @@ int nsim_dev_probe(struct nsim_bus_dev *nsim_bus_dev)
 		goto err_bpf_dev_exit;
 
 	devlink_params_publish(devlink);
+	devlink_reload_enable(devlink);
 	return 0;
 
 err_bpf_dev_exit:
@@ -865,6 +866,8 @@ void nsim_dev_remove(struct nsim_bus_dev *nsim_bus_dev)
 	struct nsim_dev *nsim_dev = dev_get_drvdata(&nsim_bus_dev->dev);
 	struct devlink *devlink = priv_to_devlink(nsim_dev);
 
+	devlink_reload_disable(devlink);
+
 	nsim_dev_reload_destroy(nsim_dev);
 
 	nsim_bpf_dev_exit(nsim_dev);
diff --git a/include/net/devlink.h b/include/net/devlink.h
index 8d6b5846822c..7891611868e4 100644
--- a/include/net/devlink.h
+++ b/include/net/devlink.h
@@ -38,8 +38,9 @@ struct devlink {
 	struct device *dev;
 	possible_net_t _net;
 	struct mutex lock;
-	bool reload_failed;
-	bool registered;
+	u8 reload_failed:1,
+	   reload_enabled:1,
+	   registered:1;
 	char priv[0] __aligned(NETDEV_ALIGN);
 };
 
@@ -824,6 +825,8 @@ void devlink_net_set(struct devlink *devlink, struct net *net);
 struct devlink *devlink_alloc(const struct devlink_ops *ops, size_t priv_size);
 int devlink_register(struct devlink *devlink, struct device *dev);
 void devlink_unregister(struct devlink *devlink);
+void devlink_reload_enable(struct devlink *devlink);
+void devlink_reload_disable(struct devlink *devlink);
 void devlink_free(struct devlink *devlink);
 int devlink_port_register(struct devlink *devlink,
 			  struct devlink_port *devlink_port,
diff --git a/net/core/devlink.c b/net/core/devlink.c
index ff53f7d29dea..2e027c9436e0 100644
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -2791,6 +2791,9 @@ static int devlink_reload(struct devlink *devlink, struct net *dest_net,
 {
 	int err;
 
+	if (!devlink->reload_enabled)
+		return -EOPNOTSUPP;
+
 	err = devlink->ops->reload_down(devlink, !!dest_net, extack);
 	if (err)
 		return err;
@@ -6308,6 +6311,8 @@ EXPORT_SYMBOL_GPL(devlink_register);
 void devlink_unregister(struct devlink *devlink)
 {
 	mutex_lock(&devlink_mutex);
+	WARN_ON(devlink_reload_supported(devlink) &&
+		devlink->reload_enabled);
 	devlink_notify(devlink, DEVLINK_CMD_DEL);
 	list_del(&devlink->list);
 	mutex_unlock(&devlink_mutex);
@@ -6315,6 +6320,41 @@ void devlink_unregister(struct devlink *devlink)
 EXPORT_SYMBOL_GPL(devlink_unregister);
 
 /**
+ *	devlink_reload_enable - Enable reload of devlink instance
+ *
+ *	@devlink: devlink
+ *
+ *	Should be called at end of device initialization
+ *	process when reload operation is supported.
+ */
+void devlink_reload_enable(struct devlink *devlink)
+{
+	mutex_lock(&devlink_mutex);
+	devlink->reload_enabled = true;
+	mutex_unlock(&devlink_mutex);
+}
+EXPORT_SYMBOL_GPL(devlink_reload_enable);
+
+/**
+ *	devlink_reload_disable - Disable reload of devlink instance
+ *
+ *	@devlink: devlink
+ *
+ *	Should be called at the beginning of device cleanup
+ *	process when reload operation is supported.
+ */
+void devlink_reload_disable(struct devlink *devlink)
+{
+	mutex_lock(&devlink_mutex);
+	/* Mutex is taken which ensures that no reload operation is in
+	 * progress while setting up forbidded flag.
+	 */
+	devlink->reload_enabled = false;
+	mutex_unlock(&devlink_mutex);
+}
+EXPORT_SYMBOL_GPL(devlink_reload_disable);
+
+/**
  *	devlink_free - Free devlink instance resources
  *
  *	@devlink: devlink
@@ -8201,7 +8241,7 @@ static void __net_exit devlink_pernet_pre_exit(struct net *net)
 			if (WARN_ON(!devlink_reload_supported(devlink)))
 				continue;
 			err = devlink_reload(devlink, &init_net, NULL);
-			if (err)
+			if (err && err != -EOPNOTSUPP)
 				pr_warn("Failed to reload devlink instance into init_net\n");
 		}
 	}