linux-kernel - Re: [PATCH RFC/RFT net-next v2 1/5] net: dsa: deny bridge VLAN with existing 8021q upper on any port

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Message-ID: <aS2qnzL2WC-sFlnJ@horms.kernel.org>
Date: Mon, 1 Dec 2025 14:47:59 +0000
From: Simon Horman <horms@...nel.org>
To: Jonas Gorski <jonas.gorski@...il.com>
Cc: Andrew Lunn <andrew@...n.ch>, Vladimir Oltean <olteanv@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Shuah Khan <shuah@...nel.org>,
	Florian Fainelli <f.fainelli@...il.com>,
	Vladimir Oltean <vladimir.oltean@....com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH RFC/RFT net-next v2 1/5] net: dsa: deny bridge VLAN with
 existing 8021q upper on any port

On Mon, Dec 01, 2025 at 11:28:13AM +0100, Jonas Gorski wrote:

...

> diff --git a/net/dsa/user.c b/net/dsa/user.c
> index f59d66f0975d..fa1fe0f1493a 100644
> --- a/net/dsa/user.c
> +++ b/net/dsa/user.c
> @@ -653,21 +653,30 @@ static int dsa_user_port_attr_set(struct net_device *dev, const void *ctx,
>  
>  /* Must be called under rcu_read_lock() */
>  static int
> -dsa_user_vlan_check_for_8021q_uppers(struct net_device *user,
> +dsa_user_vlan_check_for_8021q_uppers(struct dsa_port *dp,
>  				     const struct switchdev_obj_port_vlan *vlan)
>  {
> -	struct net_device *upper_dev;
> -	struct list_head *iter;
> +	struct dsa_switch *ds = dp->ds;
> +	struct dsa_port *other_dp;
>  
> -	netdev_for_each_upper_dev_rcu(user, upper_dev, iter) {
> -		u16 vid;
> +	dsa_switch_for_each_user_port(other_dp, ds) {
> +		struct net_device *user = other_dp->user;

Hi Jonas,

The AI robot is concerned that user may be NULL here.
And I can't convince myself that cannot be the case.

Could you take a look?

https://netdev-ai.bots.linux.dev/ai-review.html?id=3d47057e-e740-4b66-9d60-9ec2a7ee92a1#patch-0

> +		struct net_device *upper_dev;
> +		struct list_head *iter;
>  
> -		if (!is_vlan_dev(upper_dev))
> +		if (!dsa_port_bridge_same(dp, other_dp))
>  			continue;
>  
> -		vid = vlan_dev_vlan_id(upper_dev);
> -		if (vid == vlan->vid)
> -			return -EBUSY;
> +		netdev_for_each_upper_dev_rcu(user, upper_dev, iter) {
> +			u16 vid;
> +
> +			if (!is_vlan_dev(upper_dev))
> +				continue;
> +
> +			vid = vlan_dev_vlan_id(upper_dev);
> +			if (vid == vlan->vid)
> +				return -EBUSY;
> +		}
>  	}
>  
>  	return 0;

...