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Date: Fri, 07 Jun 2013 08:04:30 +0200
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From: Takashi Iwai <tiwai@suse.de>
To: Ming Lei <ming.lei@canonical.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v1 4/4] firmware loader: don't allow to request firmware via relative path
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At Fri, 7 Jun 2013 09:30:09 +0800,
Ming Lei wrote:
> 
> On Fri, Jun 7, 2013 at 3:48 AM, Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> > On Thu, Jun 06, 2013 at 08:01:50PM +0800, Ming Lei wrote:
> >> It isn't a good pratice to request firmware via relative path, also
> >> might have security issue, so don't do it.
> >
> > What would the security issue be?  You are letting the person who build
> > the kernel specify this, so they can put whatever they want in here, a
> > '..' isn't going to keep them from being able to do "bad" things if they
> > really want to.
> 
> In VM case, guest kernel might access host filesystem files via this trick,
> but not sure if it is possible.
> 
> Takashi, could you explain the security issue of relative path?

Well, I don't know, too.  My original question was what happens if you
pass a relative path to firmware_class.fw_path_para module option
(or the new kconfig)...


Takashi