netdev - Re: [PATCH net] amt: do not use overwrapped cb area

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Date: Thu, 11 Jan 2024 10:41:14 -0500
From: Jamal Hadi Salim <jhs@...atatu.com>
To: Taehee Yoo <ap420073@...il.com>
Cc: davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com, 
	edumazet@...gle.com, netdev@...r.kernel.org, paulb@...dia.com
Subject: Re: [PATCH net] amt: do not use overwrapped cb area

On Sun, Jan 7, 2024 at 9:44 AM Taehee Yoo <ap420073@...il.com> wrote:
>
> amt driver uses skb->cb for storing tunnel information.
> This job is worked before TC layer and then amt driver load tunnel info
> from skb->cb after TC layer.
> So, its cb area should not be overwrapped with CB area used by TC.
> In order to not use cb area used by TC, it skips the biggest cb
> structure used by TC, which was qdisc_skb_cb.
> But it's not anymore.
> Currently, biggest structure of TC's CB is tc_skb_cb.
> So, it should skip size of tc_skb_cb instead of qdisc_skb_cb.
>
> Fixes: ec624fe740b4 ("net/sched: Extend qdisc control block with tc control block")
> Signed-off-by: Taehee Yoo <ap420073@...il.com>


Reviewed-by: Jamal Hadi Salim <jhs@...atatu.com>

cheers,
jamal

> ---
>  drivers/net/amt.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/amt.c b/drivers/net/amt.c
> index 53415e83821c..68e79b1272f6 100644
> --- a/drivers/net/amt.c
> +++ b/drivers/net/amt.c
> @@ -11,7 +11,7 @@
>  #include <linux/net.h>
>  #include <linux/igmp.h>
>  #include <linux/workqueue.h>
> -#include <net/sch_generic.h>
> +#include <net/pkt_sched.h>
>  #include <net/net_namespace.h>
>  #include <net/ip.h>
>  #include <net/udp.h>
> @@ -80,11 +80,11 @@ static struct mld2_grec mldv2_zero_grec;
>
>  static struct amt_skb_cb *amt_skb_cb(struct sk_buff *skb)
>  {
> -       BUILD_BUG_ON(sizeof(struct amt_skb_cb) + sizeof(struct qdisc_skb_cb) >
> +       BUILD_BUG_ON(sizeof(struct amt_skb_cb) + sizeof(struct tc_skb_cb) >
>                      sizeof_field(struct sk_buff, cb));
>
>         return (struct amt_skb_cb *)((void *)skb->cb +
> -               sizeof(struct qdisc_skb_cb));
> +               sizeof(struct tc_skb_cb));
>  }
>
>  static void __amt_source_gc_work(void)
> --
> 2.34.1
>