Re: [PATCH net-next v2 2/5] ethtool: hold a reference to the netdevice around devlink compat

[Florian Fainelli <f.fainelli@gmail.com>]

On 2/22/19 11:54 AM, Jakub Kicinski wrote:
> When calling into devlink compat code make sure we have a reference
> on the netdevice on which the operation was invoked.
> 
> Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
> ---
>  net/core/ethtool.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/net/core/ethtool.c b/net/core/ethtool.c
> index 1320e8dce559..6832476dfcaf 100644
> --- a/net/core/ethtool.c
> +++ b/net/core/ethtool.c
> @@ -805,11 +805,14 @@ 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])
> +	if (!info.fw_version[0]) {
> +		dev_hold(dev);
> +		rtnl_unlock();
>  		devlink_compat_running_version(dev, info.fw_version,
>  					       sizeof(info.fw_version));
> -	rtnl_lock();
> +		rtnl_lock();
> +		dev_put(dev);
> +	}

Would it make sense to make the locking and reference holding implicit
within the compat versions of devlink_* because they use a net_device ->
devlink object manipulation as opposed to doing in the caller. We are
more or less guaranteed that the compatibility layer is used from within
ethtool.
-- 
Florian