CVE-2026-46324

In the Linux kernel, the following vulnerability has been resolved:

netfilter: nf_tables: use list_del_rcu for netlink hooks

nft_netdev_unregister_hooks and __nft_unregister_flowtable_net_hooks need
to use list_del_rcu(), this list can be walked by concurrent dumpers.

Add a new helper and use it consistently.