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 "0000:00:10.0" >/sys/bus/pci/drivers/mlxsw_spectrum2/bind
        devlink dev reload pci/0000:00:10.0 &
        echo "0000:00:10.0" >/sys/bus/pci/drivers/mlxsw_spectrum2/unbind
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>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 38 insertions, 1 deletions

diff --git a/net/core/devlink.c b/net/core/devlink.c
index f80151eeaf51..7d64660a72fc 100644
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -2699,7 +2699,7 @@ static int devlink_nl_cmd_reload(struct sk_buff *skb, struct genl_info *info)
 	struct devlink *devlink = info->user_ptr[0];
 	int err;
 
-	if (!devlink_reload_supported(devlink))
+	if (!devlink_reload_supported(devlink) || !devlink->reload_enabled)
 		return -EOPNOTSUPP;
 
 	err = devlink_resources_validate(devlink, NULL, info);
@@ -6196,6 +6196,8 @@ 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);
@@ -6203,6 +6205,41 @@ 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