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Date: Fri, 8 Dec 2023 08:11:23 -0800
From: Jakub Kicinski <kuba@kernel.org>
To: Jiri Pirko <jiri@resnulli.us>
Cc: netdev@vger.kernel.org, pabeni@redhat.com, davem@davemloft.net,
 edumazet@google.com, jacob.e.keller@intel.com, jhs@mojatatu.com,
 johannes@sipsolutions.net, andriy.shevchenko@linux.intel.com,
 amritha.nambiar@intel.com, sdf@google.com, horms@kernel.org,
 przemyslaw.kitszel@intel.com
Subject: Re: [patch net-next v5 5/9] genetlink: introduce per-sock family
 private storage
Message-ID: <20231208081123.448e4c5b@kernel.org>
In-Reply-To: <ZXMmgJHPdBUFlROg@nanopsycho>
References: <20231206182120.957225-1-jiri@resnulli.us>
	<20231206182120.957225-6-jiri@resnulli.us>
	<20231207185526.5e59ab53@kernel.org>
	<ZXMmgJHPdBUFlROg@nanopsycho>
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On Fri, 8 Dec 2023 15:21:52 +0100 Jiri Pirko wrote:
> >> +static struct genl_sk_priv *genl_sk_priv_alloc(struct genl_family *family)
> >> +{
> >> +	struct genl_sk_priv *priv;
> >> +
> >> +	priv = kzalloc(size_add(sizeof(*priv), family->sock_priv_size),
> >> +		       GFP_KERNEL);
> >> +	if (!priv)
> >> +		return ERR_PTR(-ENOMEM);
> >> +	priv->destructor = family->sock_priv_destroy;  
> >
> >family->sock_priv_destroy may be in module memory.
> >I think you need to wipe them when family goes :(  
> 
> Crap. That's a bit problematic. Family can unregister and register
> again, with user having the same sock sill opened with legitimate
> expectation of filter being applied. Don't see now how to handle this
> other then no-destroy and just kfree here in genetlink.c :/ Going back
> to v4?

When family gets removed all subs must be cleared. So the user
sock will have to resolve the mcast ID again, and re-subscribe
again to get any notification. Having to re-sub implies having
to re-add filters in my mind.