netdev - Re: RFC: disablenetwork facility. (v4)

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Message-ID: <8817.1262011044@localhost>
Date:	Mon, 28 Dec 2009 09:37:24 -0500
From:	Valdis.Kletnieks@...edu
To:	Pavel Machek <pavel@....cz>
Cc:	Michael Stone <michael@...top.org>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, linux-security-module@...r.kernel.org,
	Andi Kleen <andi@...stfloor.org>, David Lang <david@...g.hm>,
	Oliver Hartkopp <socketcan@...tkopp.net>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Bryan Donlan <bdonlan@...il.com>,
	Evgeniy Polyakov <zbr@...emap.net>,
	"C. Scott Ananian" <cscott@...ott.net>,
	James Morris <jmorris@...ei.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Bernie Innocenti <bernie@...ewiz.org>,
	Mark Seaborn <mrs@...hic-beasts.com>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	Américo Wang <xiyou.wangcong@...il.com>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	Samir Bellabes <sam@...ack.fr>,
	Casey Schaufler <casey@...aufler-ca.com>,
	"Serge E. Hallyn" <serue@...ibm.com>
Subject: Re: RFC: disablenetwork facility. (v4)

On Mon, 28 Dec 2009 11:10:06 +0100, Pavel Machek said:

> a) make disablenetwork reset to "enablenetwork" during setuid exec

That won't work either.  If you only make it 'setuid==0' binaries, you still
break 'setuid-FOO' binaries that require the net. If you just check the setuid
bit, it allows a trivial escape by creating a setuid-yourself binary and using
that to exec something else (now with network access, because we apparently
don't have a way to remember the previous setting).

> b) disallow setuid execs for tasks that have network disabled.

This is probably safer...


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