linux-kernel - Re: [PATCH] kmod: don't load module unless req process has CAP_SYS

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Date:   Mon, 15 May 2017 21:59:58 +0200
From:   Florian Westphal <fw@...len.de>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Mahesh Bandewar
         (महेश बंडेवार) <maheshb@...gle.com>,
        David Miller <davem@...emloft.net>, gregkh@...uxfoundation.org,
        mahesh@...dewar.net, mingo@...nel.org,
        linux-kernel@...r.kernel.org,
        linux-netdev <netdev@...r.kernel.org>, keescook@...omium.org,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH] kmod: don't load module unless req process has
 CAP_SYS_MODULE

Eric W. Biederman <ebiederm@...ssion.com> wrote:
> If loading the conntrack module changes the semantics of packet
> processing when nothing is configured that is a bug in the conntrack
> module.

Thats the default behaviour since forever.

modprobe nf_conntrack_ipv4 -- module_init registers netfilter hooks
and starts doing connection tracking.

You might say 'its wrong' but thats how its been for over a decade.

If you have a suggestion on how to transition to a 'sane' behaviour,
then I'm all ears.

Note however, that conntrack doesn't need any configuration currently.

Its just there once module is loaded.
We could try hooking into nftables/iptables modules that use conntrack
info to make a decision, and thats what we do now in namespaces other
than init_net.

We still do it be default in iniet_net because someone could be
doing conntrack just for purpose of ctnetlink events (conntrack -E and
friends, or flow accouting and the like).