Re: [PATCH net] seg6: ensure packet data is writable before modifying SRH and IPv6 DA

[Andrea Mayer <andrea.mayer@uniroma2.it>]

On Tue, 29 Sep 2026 11:05:02 +0800
Hangbin Liu <hangbin.liu@linux.dev> wrote:

> [snip]
>
> >  static int input_action_end_core(struct sk_buff *skb,
> >  				 struct seg6_local_lwt *slwt)
> >  {
> > +	enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
> >  	struct ipv6_sr_hdr *srh;
> > +	int err = -EINVAL;
> >  
> >  	srh = get_and_validate_srh(skb);
> >  	if (!srh)
> >  		goto drop;
> >  
> > -	advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
> > +	srh = advance_nextseg(skb, srh, &reason);
> > +	if (!srh) {
> > +		err = -ENOMEM;
> > +		goto drop;
> > +	}
>
> The srh is not used in the later function, maybe just
>
> 	if (!advance_nextseg(skb, srh, &reason)) {
> 		err = -ENOMEM;
> 		goto drop;
> 	}
>
> [snip]

Hi Hangbin,

Right. Since the patch changed advance_nextseg() to return the SRH,
I updated srh at every call site. Your form works as well where srh
is not used afterwards.

Thanks,
Andrea