Pablo Neira Ayuso says:

====================
Netfilter fixes for net

The existing attempt to resolve races between control plane and GC work
is error prone, as reported by Bien Pham <phamnnb@sea.com>, some places
forgot to call nft_set_elem_mark_busy(), leading to double-deactivation
of elements.

This series contains the following patches:

1) Do not skip expired elements during walk otherwise elements might
   never decrement the reference counter on data, leading to memleak.

2) Add a GC transaction API to replace the former attempt to deal with
   races between control plane and GC. GC worker sets on NFT_SET_ELEM_DEAD_BIT
   on elements and it creates a GC transaction to remove the expired
   elements, GC transaction could abort in case of interference with
   control plane and retried later (GC async). Set backends such as
   rbtree and pipapo also perform GC from control plane (GC sync), in
   such case, element deactivation and removal is safe because mutex
   is held then collected elements are released via call_rcu().

3) Adapt existing set backends to use the GC transaction API.

4) Update rhash set backend to set on _DEAD bit to report deleted
   elements from datapath for GC.

5) Remove old GC batch API and the NFT_SET_ELEM_BUSY_BIT.

* tag 'nf-23-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf:
  netfilter: nf_tables: remove busy mark and gc batch API
  netfilter: nft_set_hash: mark set element as dead when deleting from packet path
  netfilter: nf_tables: adapt set backend to use GC transaction API
  netfilter: nf_tables: GC transaction API to avoid race with control plane
  netfilter: nf_tables: don't skip expired elements during walk
====================

Link: https://lore.kernel.org/r/20230810070830.24064-1-pablo@netfilter.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>