netdev - Re: [PATCH v2 net] net/sched: act_pedit: really ensure the skb is writable

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Date:   Mon, 9 May 2022 08:16:37 -0400
From:   Jamal Hadi Salim <jhs@...atatu.com>
To:     Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org
Cc:     Cong Wang <xiyou.wangcong@...il.com>, Jiri Pirko <jiri@...nulli.us>
Subject: Re: [PATCH v2 net] net/sched: act_pedit: really ensure the skb is
 writable

On 2022-05-09 07:33, Paolo Abeni wrote:

[..]
>   	goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
> @@ -308,13 +320,18 @@ static int tcf_pedit_act(struct sk_buff *skb, const struct tc_action *a,
>   			 struct tcf_result *res)
>   {
>   	struct tcf_pedit *p = to_pedit(a);
> +	u32 max_offset;
>   	int i;
>   
> -	if (skb_unclone(skb, GFP_ATOMIC))
> -		return p->tcf_action;
> -
>   	spin_lock(&p->tcf_lock);
>   
> +	max_offset = (skb_transport_header_was_set(skb) ?
> +		      skb_transport_offset(skb) :
> +		      skb_network_offset(skb)) +
> +		     p->tcfp_off_max_hint;
> +	if (skb_ensure_writable(skb, min(skb->len, max_offset)))
> +		goto unlock;
> +

goto bad; would have been better so we can record it in the stats?

Other than that LGTM.
The commit message is good - but it would be better if you put that
example that triggered it.

cheers,
jamal