netdev - Re: Use-after-free in TUNSETIFF

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Message-ID: <1378910647.1538.13.camel@bwh-desktop.uk.level5networks.com>
Date:	Wed, 11 Sep 2013 15:44:07 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Stephen Hemminger <stephen@...workplumber.org>
CC:	Wannes Rombouts <wannes.rombouts@...tech.eu>,
	<davem@...emloft.net>, <jasowang@...hat.com>, <mst@...hat.com>,
	<edumazet@...gle.com>, <nhorman@...driver.com>,
	<netdev@...r.kernel.org>, Kevin Soules <kevin.soules@...tech.eu>
Subject: Re: Use-after-free in TUNSETIFF

On Tue, 2013-09-10 at 17:32 -0700, Stephen Hemminger wrote:
[...]
> [1] A user with CAP_NET_ADMIN can basically hose the system many other ways.
> Capabilities are a failed security model.
> Almost all distro's limit CAP_NET_ADMIN to root anyway.

tun uses ns_capable(), not capable().  If user namespaces are enabled
then I think any user can create their own user & net namespaces, be
'root' in those namespaces and then invoke TUNSETIFF successfully.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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