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Date: Thu, 2 Apr 2026 13:52:08 +0200
From: Florian Westphal <fw@strlen.de>
To: Steffen Klassert <steffen.klassert@secunet.com>
Cc: netdev@vger.kernel.org
Subject: Re: [PATCH ipsec 1/2] xfrm: Wait for RCU readers during policy netns
 exit
Message-ID: <ac5YaN5EJQwokOq6@strlen.de>
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Steffen Klassert <steffen.klassert@secunet.com> wrote:
> xfrm_policy_fini() frees the policy_bydst hash tables after flushing the
> policy work items and deleting all policies, but it does not wait for
> concurrent RCU readers to leave their read-side critical sections first.
> 
> The policy_bydst tables are published via rcu_assign_pointer() and are
> looked up through rcu_dereference_check(), so netns teardown must also
> wait for an RCU grace period before freeing the table memory.
> 
> Fix this by adding synchronize_rcu() before freeing the policy hash tables.
> 
> Fixes: e1e551bc5630 ("xfrm: policy: prepare policy_bydst hash for rcu lookups")

Reviewed-by: Florian Westphal <fw@strlen.de>