Subject: Re: [PATCH net-next] netfilter: arptables: use xt_entry_foreach() in copy_entries_to_user()

From: Simon Horman <[email-masked]>
Date: Thu, 22 Jan 2026 08:15:22 +0000

On Wed, Jan 21, 2026 at 11:05:21PM +0100, Florian Westphal wrote:
> Simon Horman <[email-masked]> wrote:
> > On Mon, Jan 19, 2026 at 12:07:04PM +0530, Kshitiz Bartariya wrote:
> > > Replace the manual offset-based iteration with xt_entry_foreach(),
> > > thereby removing FIXME. The byte offset semantics and user ABI
> > > are preserved.
> > > 
> > > Signed-off-by: Kshitiz Bartariya <[email-masked]>
> > > ---
> > >  net/ipv4/netfilter/arp_tables.c | 8 ++++----
> > >  1 file changed, 4 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
> > > index 1cdd9c28ab2d..9f82ce0fcaa5 100644
> > > --- a/net/ipv4/netfilter/arp_tables.c
> > > +++ b/net/ipv4/netfilter/arp_tables.c
> > > @@ -684,12 +684,11 @@ static int copy_entries_to_user(unsigned int total_size,
> > >  
> > >  	loc_cpu_entry = private->entries;
> > >  
> > > -	/* FIXME: use iterator macros --RR */
> > > -	/* ... then go back and fix counters and names */
> > > -	for (off = 0, num = 0; off < total_size; off += e->next_offset, num++){
> > > +	num = 0;
> > > +	xt_entry_foreach(e, loc_cpu_entry, total_size) {
> > >  		const struct xt_entry_target *t;
> > >  
> > > -		e = loc_cpu_entry + off;
> > > +		off = (unsigned char *)e - (unsigned char *)loc_cpu_entry;
> > 
> > This offset calculation makes me feel queasy.
> > 
> > Can the code start with off = 0 and increment it by e->next_offset
> > as the loop iterates, as was the case before this patch?
> > It would be similar to how num is handled.
> 
> I think this file should just be left alone resp. should be restricted
> to bug fixes only.  Same for ip/ip6/ebtables.
> 
> Its too early to remove this file from the tree, but I don't see
> value in making cosmetic improvements, sorry.

Thanks Florian,

No objection to that approach from my side.