From: Jiri Pirko <jiri@mellanox.com>
Date: Fri, 8 Nov 2019 21:42:43 +0100
Subject: devlink: disallow reload operation during device cleanup
Patch-mainline: v5.5-rc1
Git-commit: a0c76345e3d3dbc40c39de2e00d15a3b7eef7885
References: bsc#1154353

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>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/ethernet/mellanox/mlxsw/core.c |    4 +++-
 drivers/net/netdevsim/dev.c                |    2 ++
 net/core/devlink.c                         |    5 ++++-
 3 files changed, 9 insertions(+), 2 deletions(-)

--- 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 s
 	if (err)
 		goto err_thermal_init;
 
-	if (mlxsw_driver->params_register)
+	if (mlxsw_driver->params_register) {
 		devlink_params_publish(devlink);
+		devlink_reload_enable(devlink);
+	}
 
 	if (!reload)
 		devlink_reload_enable(devlink);
--- a/drivers/net/netdevsim/dev.c
+++ b/drivers/net/netdevsim/dev.c
@@ -864,6 +864,8 @@ void nsim_dev_remove(struct 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);
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -2791,6 +2791,9 @@ static int devlink_reload(struct devlink
 {
 	int err;
 
+	if (!devlink->reload_enabled)
+		return -EOPNOTSUPP;
+
 	err = devlink->ops->reload_down(devlink, !!dest_net, extack);
 	if (err)
 		return err;
@@ -8244,7 +8247,7 @@ static void __net_exit devlink_pernet_pr
 			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");
 		}
 	}