netdev - Re: [PATCH v7 1/6] netlink: Reverse the patch which removed filtering

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Date: Fri, 7 Jul 2023 09:59:08 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Anjali Kulkarni <anjali.k.kulkarni@...cle.com>
Cc: davem@...emloft.net, david@...es.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, zbr@...emap.net, brauner@...nel.org,
        johannes@...solutions.net, ecree.xilinx@...il.com, leon@...nel.org,
        keescook@...omium.org, socketcan@...tkopp.net, petrm@...dia.com,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v7 1/6] netlink: Reverse the patch which removed filtering

* Anjali Kulkarni <anjali.k.kulkarni@...cle.com> [691231 23:00]:
> To use filtering at the connector & cn_proc layers, we need to enable
> filtering in the netlink layer. This reverses the patch which removed
> netlink filtering.
> 
> Signed-off-by: Anjali Kulkarni <anjali.k.kulkarni@...cle.com>

Reviewed-by: Liam R. Howlett <Liam.Howlett@...cle.com>

> ---
>  include/linux/netlink.h  |  5 +++++
>  net/netlink/af_netlink.c | 27 +++++++++++++++++++++++++--
>  2 files changed, 30 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/netlink.h b/include/linux/netlink.h
> index 19c0791ed9d5..d73cfe5b6bc2 100644
> --- a/include/linux/netlink.h
> +++ b/include/linux/netlink.h
> @@ -227,6 +227,11 @@ bool netlink_strict_get_check(struct sk_buff *skb);
>  int netlink_unicast(struct sock *ssk, struct sk_buff *skb, __u32 portid, int nonblock);
>  int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, __u32 portid,
>  		      __u32 group, gfp_t allocation);
> +int netlink_broadcast_filtered(struct sock *ssk, struct sk_buff *skb,
> +			       __u32 portid, __u32 group, gfp_t allocation,
> +			       int (*filter)(struct sock *dsk,
> +					     struct sk_buff *skb, void *data),
> +			       void *filter_data);
>  int netlink_set_err(struct sock *ssk, __u32 portid, __u32 group, int code);
>  int netlink_register_notifier(struct notifier_block *nb);
>  int netlink_unregister_notifier(struct notifier_block *nb);
> diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
> index 3a1e0fd5bf14..e75e5156e4ac 100644
> --- a/net/netlink/af_netlink.c
> +++ b/net/netlink/af_netlink.c
> @@ -1432,6 +1432,8 @@ struct netlink_broadcast_data {
>  	int delivered;
>  	gfp_t allocation;
>  	struct sk_buff *skb, *skb2;
> +	int (*tx_filter)(struct sock *dsk, struct sk_buff *skb, void *data);
> +	void *tx_data;
>  };
>  
>  static void do_one_broadcast(struct sock *sk,
> @@ -1485,6 +1487,13 @@ static void do_one_broadcast(struct sock *sk,
>  			p->delivery_failure = 1;
>  		goto out;
>  	}
> +
> +	if (p->tx_filter && p->tx_filter(sk, p->skb2, p->tx_data)) {
> +		kfree_skb(p->skb2);
> +		p->skb2 = NULL;
> +		goto out;
> +	}
> +
>  	if (sk_filter(sk, p->skb2)) {
>  		kfree_skb(p->skb2);
>  		p->skb2 = NULL;
> @@ -1507,8 +1516,12 @@ static void do_one_broadcast(struct sock *sk,
>  	sock_put(sk);
>  }
>  
> -int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, u32 portid,
> -		      u32 group, gfp_t allocation)
> +int netlink_broadcast_filtered(struct sock *ssk, struct sk_buff *skb,
> +			       u32 portid,
> +			       u32 group, gfp_t allocation,
> +			       int (*filter)(struct sock *dsk,
> +					     struct sk_buff *skb, void *data),
> +			       void *filter_data)
>  {
>  	struct net *net = sock_net(ssk);
>  	struct netlink_broadcast_data info;
> @@ -1527,6 +1540,8 @@ int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, u32 portid,
>  	info.allocation = allocation;
>  	info.skb = skb;
>  	info.skb2 = NULL;
> +	info.tx_filter = filter;
> +	info.tx_data = filter_data;
>  
>  	/* While we sleep in clone, do not allow to change socket list */
>  
> @@ -1552,6 +1567,14 @@ int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, u32 portid,
>  	}
>  	return -ESRCH;
>  }
> +EXPORT_SYMBOL(netlink_broadcast_filtered);
> +
> +int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, u32 portid,
> +		      u32 group, gfp_t allocation)
> +{
> +	return netlink_broadcast_filtered(ssk, skb, portid, group, allocation,
> +					  NULL, NULL);
> +}
>  EXPORT_SYMBOL(netlink_broadcast);
>  
>  struct netlink_set_err_data {
> -- 
> 2.41.0
>