netdev - Re: [RFC PATCH v1 1/2] lsm: Add hooks to the TUN driver

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Date:	Wed, 5 Aug 2009 17:58:38 -0400
From:	Paul Moore <paul.moore@...com>
To:	"Serge E. Hallyn" <serue@...ibm.com>, eparis@...hat.com
Cc:	netdev@...r.kernel.org, linux-security-module@...r.kernel.org,
	selinux@...ho.nsa.gov
Subject: Re: [RFC PATCH v1 1/2] lsm: Add hooks to the TUN driver

On Wednesday 05 August 2009 10:13:50 am Serge E. Hallyn wrote:
> Quoting Paul Moore (paul.moore@...com):

[NOTE: my email has been out all day due to some mysterious FS issue so my 
apologies for not replying sooner]

...

> The checks before and after this patch are not equivalent.  Post-patch,
> one must always have CAP_NET_ADMIN to do the attach, whereas pre-patch
> you only needed those if current_cred() did not own the tun device.  Is
> that intentional?

Nope, just a goof on my part; I misread the booleans and haven't fully tested 
the patch yet so it slipped out, thanks for catching it.  This brings up a 
good point, would we rather move the TUN owner/group checks into the cap_tun_* 
functions or move the capable() call back into the TUN driver?  The answer 
wasn't clear to me when I was looking at the code before and the uniqueness of 
the TUN driver doesn't help much in this regard.

> Also as Eric said this patch needs to set the cap_ hooks.  This patch
> isn't yet introducing the selinux hooks, so iiuc actually this patch should
> always oops if CONFIG_SECURITY=y.

Yep, another symptom of not enough testing as I mentioned out in the original 
posting, thanks to both of you for pointing this out ... now somebody just 
needs to fix Rawhide so I can actually get a KVM instance running :)

-- 
paul moore
linux @ hp

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