Re: [PATCH nf] netfilter: ipset: let destroy callbacks adjust ext mem size

[Jozsef Kadlecsik <kadlec@netfilter.org>]

On Thu, 6 Aug 2026, Florian Westphal wrote:

> For bitmap this change makes no difference, because destructors are
> called synchronously.
> 
> List type however calls them via call_rcu() so accounting decrement can
> happen after list_set_flush() set ext_size to 0.
> 
> 'set->elements = 0' can be removed for the same reason in the list type
> case, it calls 'set->elements--' for each element.
> 
> Fixes: 9e41f26a505c ("netfilter: ipset: Count non-static extension memory for userspace")
> Suggested-by: Jozsef Kadlecsik <kadlec@netfilter.org>
> Signed-off-by: Florian Westphal <fw@strlen.de>

Acked-by: Jozsef Kadlecsik <kadlec@netfilter.org>

Best regards,
Jozsef
> ---
>  sashiko: list_set_uadd() may call list_set_replace() and
>  then erronously increments set->elements, causing a counter
>  drift. This bug will be resolved in a different patch.
> 
>  net/netfilter/ipset/ip_set_bitmap_gen.h | 2 +-
>  net/netfilter/ipset/ip_set_list_set.c   | 3 +--
>  2 files changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/net/netfilter/ipset/ip_set_bitmap_gen.h b/net/netfilter/ipset/ip_set_bitmap_gen.h
> index 226fdf17b683..d6a7e6604542 100644
> --- a/net/netfilter/ipset/ip_set_bitmap_gen.h
> +++ b/net/netfilter/ipset/ip_set_bitmap_gen.h
> @@ -77,7 +77,7 @@ mtype_flush(struct ip_set *set)
>  		mtype_ext_cleanup(set);
>  	bitmap_zero(map->members, map->elements);
>  	set->elements = 0;
> -	atomic64_set(&set->ext_size, 0);
> +	DEBUG_NET_WARN_ON_ONCE(atomic64_read(&set->ext_size) > 0);
>  }
>  
>  /* Calculate the actual memory size of the set data */
> diff --git a/net/netfilter/ipset/ip_set_list_set.c b/net/netfilter/ipset/ip_set_list_set.c
> index 56626f4943a9..b4967a9d82b0 100644
> --- a/net/netfilter/ipset/ip_set_list_set.c
> +++ b/net/netfilter/ipset/ip_set_list_set.c
> @@ -423,8 +423,7 @@ list_set_flush(struct ip_set *set)
>  
>  	list_for_each_entry_safe(e, n, &map->members, list)
>  		list_set_del(set, e);
> -	set->elements = 0;
> -	atomic64_set(&set->ext_size, 0);
> +	DEBUG_NET_WARN_ON_ONCE(set->elements > 0);
>  }
>  
>  static void
> -- 
> 2.54.0
> 
> 

-- 
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Address: Wigner Research Centre for Physics
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