Subject: Re: [patch net-next v2 01/28] net: dev: Check CHANGEUPPER notifier return value

From: John Fastabend <[email-masked]>
Date: Wed, 02 Dec 2015 15:20:50 -0800

On 15-12-02 12:07 PM, Jiri Pirko wrote:
> From: Ido Schimmel <[email-masked]>
> 
> switchdev drivers reflect the newly requested topology to hardware when
> CHANGEUPPER is received, after software links were already formed.
> However, the operation can fail and user will not be notified, as the
> return value of the notifier is not checked.
> 
> Add this check and rollback software links if necessary.
> 
> Signed-off-by: Ido Schimmel <[email-masked]>
> Signed-off-by: Jiri Pirko <[email-masked]>
> ---
> v1->v2:
> -new patch
> ---
>  net/core/dev.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 5df6cbc..df33f82 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -5490,8 +5490,11 @@ static int __netdev_upper_dev_link(struct net_device *dev,
>  			goto rollback_lower_mesh;
>  	}
>  
> -	call_netdevice_notifiers_info(NETDEV_CHANGEUPPER, dev,
> -				      &changeupper_info.info);
> +	ret = call_netdevice_notifiers_info(NETDEV_CHANGEUPPER, dev,
> +					    &changeupper_info.info);
> +	if (ret)
> +		goto rollback_lower_mesh;
> +

hmm small nit (take it or leave it) but I think it would be more
correct if this was

	if (ret == NOTIFY_BAD)
		goto rollback_lower_mesh;

It seems that NOTIFY_DONE, NOTIFY_OK and NOTIFY_STOP_MASK would be
valid return codes that don't indicate an error. However seeing I
couldn't find any cases of NOTIFY_OK/NOTIFY_STOP_MASK from the
CHANGEUPPER event it doesn't matter in practice.

Thanks,
John

>  	return 0;
>  rollback_lower_mesh: