netdev - Re: [PATCH 2/2] net: Implement SO_PASSCGROUP to enable passing cgroup path

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Message-Id: <20140423.132955.671992126955940387.davem@davemloft.net>
Date:	Wed, 23 Apr 2014 13:29:55 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	vgoyal@...hat.com
Cc:	luto@...capital.net, tj@...nel.org, dwalsh@...hat.com,
	linux-kernel@...r.kernel.org, lpoetter@...hat.com,
	ssorce@...hat.com, cgroups@...r.kernel.org, kay@...hat.com,
	netdev@...r.kernel.org
Subject: Re: [PATCH 2/2] net: Implement SO_PASSCGROUP to enable passing
 cgroup path

From: Vivek Goyal <vgoyal@...hat.com>
Date: Wed, 23 Apr 2014 12:45:37 -0400

> On Tue, Apr 15, 2014 at 08:47:54PM -0700, Andy Lutomirski wrote:
> 
> [..]
>> Here's an attack against SO_PASSCGROUP, as you implemented it: connect
>> a socket and get someone else to write(2) to it.  This isn't very
>> hard.  Now you've impersonated.
> 
> If this is a problem then I think kernel requires fixing. Because kernel
> will apply all resource management policies based on the cgroup at write(2)
> time and not based on open() time.

Anyways, this is not even worth discussing.

We already agreed that the cgroup passed at write time with SO_PASSGROUP
enabled should be the socket creation time cgroup.

Just like SO_PASSCRED does.

The identity given is thus the one at open() time.
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