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Date: Thu, 12 Sep 2024 16:27:18 +0200
From: Florian Westphal <fw@strlen.de>
To: Phil Sutter <phil@nwl.cc>, Florian Westphal <fw@strlen.de>,
	Pablo Neira Ayuso <pablo@netfilter.org>,
	netfilter-devel@vger.kernel.org, Eric Garver <e@erig.me>
Subject: Re: [nf-next PATCH v3 01/16] netfilter: nf_tables: Keep deleted
 flowtable hooks until after RCU
Message-ID: <20240912142718.GD2892@breakpoint.cc>
References: <20240912122148.12159-1-phil@nwl.cc>
 <20240912122148.12159-2-phil@nwl.cc>
 <20240912133255.GB2892@breakpoint.cc>
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Phil Sutter <phil@nwl.cc> wrote:
> > nf_tables_flowtable_destroy() is called after the hook has been
> > unregisted (detached from nf_hook list) and rcu grace period elapsed.
> 
> Yes, I didn't find a caller which didn't synchronize_rcu() before
> calling it. Same applies to chain hooks, right?

Sigh, there is nft_flowtable_find_dev() which iterates the nft_hook
list from packet path.

So the syncrhonize_rcu is irrelevant as long as the entry
is linked up and this patch is correct as-is.

 list_del_rcu(&hook->list);
 kfree(hook);

is illegal, and I think this should add a helper that unlinks
and then frees the entry via kfree_rcu and converts all instances
of this pattern.