netdev - Re: [PATCH net-next] nfnetlink_queue: enable PID info retrieval

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Date:	Fri, 10 Jun 2016 08:40:34 +0200
From:	Daniel Wagner <daniel.wagner@...-carit.de>
To:	Daniel Borkmann <daniel@...earbox.net>,
	Florian Westphal <fw@...len.de>,
	Saeed Mahameed <saeedm@...lanox.com>
CC:	"David S. Miller" <davem@...emloft.net>, <netdev@...r.kernel.org>,
	<netfilter-devel@...r.kernel.org>,
	Yevgeny Petrilin <yevgenyp@...lanox.com>,
	Andre Melkoumian <andre@...lanox.com>,
	Matthew Finlay <matt@...lanox.com>,
	Pablo Neira Ayuso <pablo@...filter.org>,
	Patrick McHardy <kaber@...sh.net>,
	Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
	<john.fastabend@...il.com>, <hannes@...essinduktion.org>,
	<tj@...nel.org>, <viro@...iv.linux.org.uk>
Subject: Re: [PATCH net-next] nfnetlink_queue: enable PID info retrieval

Hi Daniel,

> [ Cc'ing John, Daniel, et al ]
> 
> Btw, while I just looked at scm_detach_fds(), I think commits ...
> 
>  * 48a87cc26c13 ("net: netprio: fd passed in SCM_RIGHTS datagram not set
> correctly")
>  * d84295067fc7 ("net: net_cls: fd passed in SCM_RIGHTS datagram not set
> correctly")
> 
> ... might not be correct, maybe I'm missing something ...? Lets say
> process A
> has a socket fd that it sends via SCM_RIGHTS to process B. Process A was
> the
> one that called sk_alloc() originally. Now in scm_detach_fds() we
> install a new
> fd for process B pointing to the same sock (file's private_data) and
> above commits
> update the cached socket cgroup data for net_cls/net_prio to the new
> process B.
> So, if process A for example still sends data over that socket, skbs
> will then
> wrongly match on B's cgroup membership instead of A's, no?

I can't remember the details right now (need to read up again but I wont
have time till Wednesday).

>From your analysis I would say that is not the desired effect. A should
match against its own cgroup and not the one of B.

cheers,
daniel