linux-kernel - Re: [PATCH net-next] pppoe: drop PACKET_OTHERHOST before skb_share

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Message-ID: <aFkzYKBU/c8aub5Q@debian>
Date: Mon, 23 Jun 2025 12:58:40 +0200
From: Guillaume Nault <gnault@...hat.com>
To: Qingfang Deng <dqfext@...il.com>
Cc: linux-ppp@...r.kernel.org, Michal Ostrowski <mostrows@...thlink.net>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] pppoe: drop PACKET_OTHERHOST before
 skb_share_check()

On Mon, Jun 23, 2025 at 11:34:31AM +0800, Qingfang Deng wrote:
> Align with ip_rcv() by dropping PACKET_OTHERHOST packets before
> calling skb_share_check(). This avoids unnecessary skb processing
> for packets that will be discarded anyway.
> 
> Signed-off-by: Qingfang Deng <dqfext@...il.com>
> ---
>  drivers/net/ppp/pppoe.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c
> index 68e631718ab0..410effa42ade 100644
> --- a/drivers/net/ppp/pppoe.c
> +++ b/drivers/net/ppp/pppoe.c
> @@ -372,9 +372,6 @@ static int pppoe_rcv_core(struct sock *sk, struct sk_buff *skb)
>  	 * can't change.
>  	 */
>  
> -	if (skb->pkt_type == PACKET_OTHERHOST)
> -		goto abort_kfree;
> -
>  	if (sk->sk_state & PPPOX_BOUND) {
>  		ppp_input(&po->chan, skb);
>  	} else if (sk->sk_state & PPPOX_RELAY) {
> @@ -418,6 +415,9 @@ static int pppoe_rcv(struct sk_buff *skb, struct net_device *dev,
>  	struct pppoe_net *pn;
>  	int len;
>  
> +	if (skb->pkt_type == PACKET_OTHERHOST)
> +		goto drop;
> +
>  	skb = skb_share_check(skb, GFP_ATOMIC);
>  	if (!skb)
>  		goto out;

Agree. You can also refine the condition and reject broadcast packets
by using "if (skb->pkt_type != PACKET_HOST)". PPPoE session packets
should always be unicast.

Acked-by: Guillaume Nault <gnault@...hat.com>