netdev - Re: [flame^Wreview] net: netprio_cgroup: rework update socket logic

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Date:	Mon, 13 Aug 2012 10:31:22 -0700
From:	John Fastabend <john.r.fastabend@...el.com>
To:	Al Viro <viro@...IV.linux.org.uk>
CC:	netdev@...r.kernel.org, David Miller <davem@...emloft.net>,
	Neil Horman <nhorman@...driver.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [flame^Wreview] net: netprio_cgroup: rework update socket logic

On 8/13/2012 10:01 AM, Al Viro wrote:
> On Mon, Aug 13, 2012 at 09:58:12AM -0700, John Fastabend wrote:
>> [...]
>>
>>> HOWEVER, it still doesn't address more fundamental problem - somebody
>>> creating a socket and passing it to you in SCM_RIGHTS datagram will
>>> leave you with a socket you can do IO on, still tagged according to who
>>> had created it.
>>>
>>> AFAICS, the whole point of that exercise was to allow third-party changing
>>> the priorities of traffic on sockets already created by a process we now
>>> move to a different cgroup.  Consider e.g. this:
>>
>> Correct that is the point of the exercise.
>>
>> To fix this specific case we could add a call to sock_update_netprioidx
>> in scm_recv to set the sk_cgrp_prioidx value.
>
> On every received descriptor, that is?  Eeek...
>

We are already iterating through the files in scm_detach_fds called from
scm_recv(). This would be an extra (file->f_op == &socket_file_ops)
check here and then the sock update.
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