Date: Sun, 10 Jan 2010 17:40:10 -0500
From: Michael Stone <michael@laptop.org>
To: Pavel Machek <pavel@ucw.cz>
Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
       linux-security-module@vger.kernel.org, Andi Kleen <andi@firstfloor.org>,
       David Lang <david@lang.hm>, Oliver Hartkopp <socketcan@hartkopp.net>,
       Alan Cox <alan@lxorguk.ukuu.org.uk>,
       Herbert Xu <herbert@gondor.apana.org.au>,
       Valdis Kletnieks <Valdis.Kletnieks@vt.edu>,
       Bryan Donlan <bdonlan@gmail.com>, Evgeniy Polyakov <zbr@ioremap.net>,
       "C. Scott Ananian" <cscott@cscott.net>,
       James Morris <jmorris@namei.org>,
       "Eric W. Biederman" <ebiederm@xmission.com>,
       Bernie Innocenti <bernie@codewiz.org>,
       Mark Seaborn <mrs@mythic-beasts.com>,
       Randy Dunlap <randy.dunlap@oracle.com>,
       =?iso-8859-1?Q?Am=E9rico?= Wang <xiyou.wangcong@gmail.com>,
       Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
       Samir Bellabes <sam@synack.fr>,
       Casey Schaufler <casey@schaufler-ca.com>,
       "Serge E. Hallyn" <serue@us.ibm.com>, Pavel Machek <pavel@ucw.cz>,
       Al Viro <viro@ZenIV.linux.org.uk>, Michael Stone <michael@laptop.org>
Subject: Re: [PATCH 2/3] Security: Implement disablenetwork semantics. (v4)
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Pavel Machek wrote:

> You can trivialy make disablenetwork disable setuid exec, too. That
> will introduce better isolation facilities, but not introduce any new
> security problems.
> 
> For some reason, you don't want to do the obviously right thing.

I don't want to do it because it's not "obviously right" to me: I *have* setuid
programs that I want to be able to raise privileges when network-disabled.
I *don't have* any setuid programs that will be harmed by disablenetwork.

Examples of software that I want to be able to gain privileges normally include:

   rainbow, which requires privilege in order to add new accounts to the system
   and in order to call setuid() but which does not require networking
   privileges.

   qmail-queue, which uses setuid to deliver mail that it reads from fd 0 to
   local users

   and other old favorites like mount, fusermount, X, and, presumably, any audio
   software that wants to go realtime.

Kind regards,

Michael
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