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Date:   Mon, 26 Jul 2021 00:52:00 +0200
From:   Florian Westphal <fw@strlen.de>
To:     Casey Schaufler <casey@schaufler-ca.com>
Cc:     Florian Westphal <fw@strlen.de>, Paul Moore <paul@paul-moore.com>,
        Paolo Abeni <pabeni@redhat.com>, netdev@vger.kernel.org,
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        Jakub Kicinski <kuba@kernel.org>,
        Eric Dumazet <edumazet@google.com>,
        linux-security-module@vger.kernel.org, selinux@vger.kernel.org
Subject: Re: [PATCH RFC 0/9] sk_buff: optimize layout for GRO
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Casey Schaufler <casey@schaufler-ca.com> wrote:
> RedHat and android use SELinux and will want this. Ubuntu doesn't
> yet, but netfilter in in the AppArmor task list. Tizen definitely
> uses it with Smack. The notion that security modules are only used
> in fringe cases is antiquated. 

I was not talking about LSM in general, I was referring to the
extended info that Paul mentioned.

If thats indeed going to be used on every distro then skb extensions
are not suitable for this, it would result in extr akmalloc for every
skb.

> > It certainly makes more sense to me than doing lookups
> > in a hashtable based on a ID
> 
> Agreed. The data burden required to support a hash scheme
> for the security module stacking case is staggering.

It depends on the type of data (and its lifetime).

I suspect you have something that is more like skb->dev/dst,
i.e. reference to object that persists after the skb is free'd.