devlink: hold a reference to the netdevice around ethtool compat

When ethtool is calling into devlink compat code make sure we have
a reference on the netdevice on which the operation was invoked.

v3: move the hold/lock logic into devlink_compat_* functions (Florian)

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/devlink.c

@@ -6430,6 +6430,9 @@ void devlink_compat_running_version(struct net_device *dev,
 {
 	struct devlink *devlink;
 
+	dev_hold(dev);
+	rtnl_unlock();
+
 	mutex_lock(&devlink_mutex);
 	devlink = netdev_to_devlink(dev);
 	if (!devlink || !devlink->ops || !devlink->ops->info_get)
@@ -6440,6 +6443,9 @@ void devlink_compat_running_version(struct net_device *dev,
 	mutex_unlock(&devlink->lock);
 unlock_list:
 	mutex_unlock(&devlink_mutex);
+
+	rtnl_lock();
+	dev_put(dev);
 }
 
 int devlink_compat_flash_update(struct net_device *dev, const char *file_name)
@@ -6447,6 +6453,9 @@ int devlink_compat_flash_update(struct net_device *dev, const char *file_name)
 	struct devlink *devlink;
 	int ret = -EOPNOTSUPP;
 
+	dev_hold(dev);
+	rtnl_unlock();
+
 	mutex_lock(&devlink_mutex);
 	devlink = netdev_to_devlink(dev);
 	if (!devlink || !devlink->ops || !devlink->ops->flash_update)
@@ -6457,6 +6466,10 @@ int devlink_compat_flash_update(struct net_device *dev, const char *file_name)
 	mutex_unlock(&devlink->lock);
 unlock_list:
 	mutex_unlock(&devlink_mutex);
+
+	rtnl_lock();
+	dev_put(dev);
+
 	return ret;
 }
 

net/core/ethtool.c

@@ -805,11 +805,9 @@ static noinline_for_stack int ethtool_get_drvinfo(struct net_device *dev,
 	if (ops->get_eeprom_len)
 		info.eedump_len = ops->get_eeprom_len(dev);
 
-	rtnl_unlock();
 	if (!info.fw_version[0])
 		devlink_compat_running_version(dev, info.fw_version,
 					       sizeof(info.fw_version));
-	rtnl_lock();
 
 	if (copy_to_user(useraddr, &info, sizeof(info)))
 		return -EFAULT;
@@ -2040,15 +2038,8 @@ static noinline_for_stack int ethtool_flash_device(struct net_device *dev,
 		return -EFAULT;
 	efl.data[ETHTOOL_FLASH_MAX_FILENAME - 1] = 0;
 
-	if (!dev->ethtool_ops->flash_device) {
-		int ret;
-
-		rtnl_unlock();
-		ret = devlink_compat_flash_update(dev, efl.data);
-		rtnl_lock();
-
-		return ret;
-	}
+	if (!dev->ethtool_ops->flash_device)
+		return devlink_compat_flash_update(dev, efl.data);
 
 	return dev->ethtool_ops->flash_device(dev, &efl);
 }