netdev - Re: [PATCH net-next v5 02/10] net: sched: act

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Date: Wed, 26 Jun 2024 16:28:01 +0200
From: Eelco Chaudron <echaudro@...hat.com>
To: Adrian Moreno <amorenoz@...hat.com>
Cc: netdev@...r.kernel.org, aconole@...hat.com, horms@...nel.org,
 i.maximets@....org, dev@...nvswitch.org, Jamal Hadi Salim <jhs@...atatu.com>,
 Cong Wang <xiyou.wangcong@...il.com>, Jiri Pirko <jiri@...nulli.us>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v5 02/10] net: sched: act_sample: add action
 cookie to sample

On 25 Jun 2024, at 22:51, Adrian Moreno wrote:

> If the action has a user_cookie, pass it along to the sample so it can
> be easily identified.
>
> Signed-off-by: Adrian Moreno <amorenoz@...hat.com>
> ---
>  net/sched/act_sample.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/net/sched/act_sample.c b/net/sched/act_sample.c
> index a69b53d54039..2ceb4d141b71 100644
> --- a/net/sched/act_sample.c
> +++ b/net/sched/act_sample.c
> @@ -167,7 +167,9 @@ TC_INDIRECT_SCOPE int tcf_sample_act(struct sk_buff *skb,
>  {
>  	struct tcf_sample *s = to_sample(a);
>  	struct psample_group *psample_group;
> +	u8 cookie_data[TC_COOKIE_MAX_SIZE];
>  	struct psample_metadata md = {};
> +	struct tc_cookie *user_cookie;
>  	int retval;
>
>  	tcf_lastuse_update(&s->tcf_tm);
> @@ -189,6 +191,16 @@ TC_INDIRECT_SCOPE int tcf_sample_act(struct sk_buff *skb,
>  		if (skb_at_tc_ingress(skb) && tcf_sample_dev_ok_push(skb->dev))
>  			skb_push(skb, skb->mac_len);
>
> +		rcu_read_lock();
> +		user_cookie = rcu_dereference(a->user_cookie);
> +		if (user_cookie) {
> +			memcpy(cookie_data, user_cookie->data,
> +			       user_cookie->len);

Maybe I’m over paranoid, but can we assume user_cookie->len, will not be larger than TC_COOKIE_MAX_SIZE?
Or should we do something like min(user_cookie->len, sizeof(cookie_data))

> +			md.user_cookie = cookie_data;
> +			md.user_cookie_len = user_cookie->len;
> +		}
> +		rcu_read_unlock();
> +
>  		md.trunc_size = s->truncate ? s->trunc_size : skb->len;
>  		psample_sample_packet(psample_group, skb, s->rate, &md);
>
> -- 
> 2.45.1