linux-kernel - Re: security review needed - Re: [PATCH] ohci: Turn remote DMA support into a module parameter

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Message-ID: <20140112185921.3753b042@stein>
Date:	Sun, 12 Jan 2014 18:59:21 +0100
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	Stefan Richter <stefanr@...6.in-berlin.de>
Cc:	Lubomir Rintel <lkundrak@...sk>, linux-kernel@...r.kernel.org,
	linux1394-devel@...ts.sourceforge.net,
	Dave Hansen <dave.hansen@...ux.intel.com>, security@...nel.org
Subject: Re: security review needed - Re: [PATCH] ohci: Turn remote DMA
 support into a module parameter

On Dec 23 Stefan Richter wrote:
> On Dec 22 Lubomir Rintel wrote:
> > This makes it possible to debug kernel over FireWire without the need to
> > recompile it.
> > 
> > Cc: Stefan Richter <stefanr@...6.in-berlin.de>
> > Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> > Signed-off-by: Lubomir Rintel <lkundrak@...sk>
> 
> Looks good to me.  A load-time option is preferable over a compile-time
> option not only from the POV of the debugging use case, but also from the
> maintenance POV.
> 
> It weakens security in two scenarios though, AFAICS:
> 
> A)
>   - There are firewire-ohci and firewire-sbp2 installed on the machine,
>   - the attacker cannot upload code
>   - but can load kernel modules
>   - and has physical access to a 1394 port
>   - and is not able to run a minimal SBP-2 target on the remote 1394 end.
> 
> B)
>   - There is firewire-ohci but not firewire-sbp2 installed on the machine,
>   - the attacker cannot upload code
>   - but can load kernel modules
>   - and has physical access to a 1394 port.
> 
> (In both scenarios, the attacker additionally has to be able to /un/load
> kernel modules if firewire-ohci was loaded already before the attack.)
> 
> That's both quite specific.  Hence the security impact of this patch is
> negligible in my opinion.  Any other opinions or insights into it?

Since there were no objections, I committed it to linux1394.git master
and for-next now.
-- 
Stefan Richter
-=====-====- ---= -==--
http://arcgraph.de/sr/
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