netdev - Re: [PATCH net] net/sched: act_ct: Take per-cb reference to tcf_ct_flow

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Date: Fri, 8 Dec 2023 15:40:35 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: <jhs@...atatu.com>, <pablo@...filter.org>
Cc: Vlad Buslov <vladbu@...dia.com>, <davem@...emloft.net>,
 <pabeni@...hat.com>, <edumazet@...gle.com>, <netdev@...r.kernel.org>,
 <louis.peens@...igine.com>, <yinjun.zhang@...igine.com>,
 <simon.horman@...igine.com>, <jiri@...nulli.us>,
 <xiyou.wangcong@...il.com>, Paul Blakey <paulb@...dia.com>
Subject: Re: [PATCH net] net/sched: act_ct: Take per-cb reference to
 tcf_ct_flow_table

On Tue, 5 Dec 2023 18:25:54 +0100 Vlad Buslov wrote:
> The referenced change added custom cleanup code to act_ct to delete any
> callbacks registered on the parent block when deleting the
> tcf_ct_flow_table instance. However, the underlying issue is that the
> drivers don't obtain the reference to the tcf_ct_flow_table instance when
> registering callbacks which means that not only driver callbacks may still
> be on the table when deleting it but also that the driver can still have
> pointers to its internal nf_flowtable and can use it concurrently which
> results either warning in netfilter[0] or use-after-free.
> 
> Fix the issue by taking a reference to the underlying struct
> tcf_ct_flow_table instance when registering the callback and release the
> reference when unregistering. Expose new API required for such reference
> counting by adding two new callbacks to nf_flowtable_type and implementing
> them for act_ct flowtable_ct type. This fixes the issue by extending the
> lifetime of nf_flowtable until all users have unregistered.

Some acks would be good here - Pablo, Jamal?
-- 
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