linux-kernel - Re: RFC: disablenetwork facility. (v4)

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Message-ID: <m1my10tbcu.fsf@fess.ebiederm.org>
Date:	Wed, 30 Dec 2009 13:12:33 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	"Serge E. Hallyn" <serue@...ibm.com>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Benny Amorsen <benny+usenet@...rsen.dk>,
	Bryan Donlan <bdonlan@...il.com>,
	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>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	Evgeniy Polyakov <zbr@...emap.net>,
	"C. Scott Ananian" <cscott@...ott.net>,
	James Morris <jmorris@...ei.org>,
	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>,
	Pavel Machek <pavel@....cz>, Al Viro <viro@...iv.linux.org.uk>
Subject: Re: RFC: disablenetwork facility. (v4)

"Serge E. Hallyn" <serue@...ibm.com> writes:

> Quoting Eric W. Biederman (ebiederm@...ssion.com):
>> "Serge E. Hallyn" <serue@...ibm.com> writes:
>> 
>> >> In common cap we drop the new capabilities if we are being ptraced.
>> >> Look for brm->unsafe.
>> >
>> > Yes - that isn't the issue.
>> 
>> Right.  Sorry.  I saw that we set unsafe and totally
>> missed that we don't act on it in that case.
>> 
>> > It goes back to finding a way to figure out what is inside the
>> > file when the installer obviously thought we shouldn't be able
>> > to read the file.
>> >
>> > Do we care?  <shrug>
>> 
>> <shrug>
>> 
>> I expect two lines of testing bprm->unsafe and failing
>> at the right point would solve that. 
>
> But what is the right response?  Prevent excecution?  Stop the
> tracer?  Enter some one-shot mode where the whole exec appears
> as one step, but tracing continues if execution continues on a
> dumpable file?

The whole exec should already appear as one step.

The right response is to either fail the exec or disable
the tracer.  Since the other case drops privs.  I expect
failing the exec is the simplest and most consistent thing
we can do.

Eric
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