From: Oliver Neukum <oliver@neukum.org>
To: Pavel Machek <pavel@ucw.cz>
Subject: Re: [PATCH] zero disk pages used by swsusp on resume
Date: Mon, 11 Apr 2005 12:37:45 +0200
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Cc: Andreas Steinmetz <ast@domdv.de>,
       Linux Kernel Mailinglist <linux-kernel@vger.kernel.org>
References: <42592697.8060909@domdv.de> <200504102203.29602.oliver@neukum.org> <20050410201455.GA21568@elf.ucw.cz>
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Am Sonntag, 10. April 2005 22:14 schrieb Pavel Machek:
> Hi!
> 
> > > Oliver Neukum wrote:
> > > > What is the point in doing so after they've rested on the disk for ages?
> > > 
> > > The point is not physical access to the disk but data gathering after
> > > resume or reboot.
> > 
> > After resume or reboot normal access control mechanisms will work
> > again. Those who can read a swap partition under normal circumstances
> > can also read /dev/kmem. It seems to me like you are putting an extra
> > lock on a window on the third floor while leaving the front door open.
> 
> Andreas is right, his patches are needed.
> 
> Currently, if your laptop is stolen after resume, they can still data
> in swsusp image.
> 
> Zeroing the swsusp pages helps a lot here, because at least they are
> not getting swsusp image data without heavy tools. [Or think root
> compromise month after you used swsusp.]
> 
> Encrypting swsusp image is of course even better, because you don't
> have to write large ammounts of zeros to your disks during resume ;-).

Not only is it better, it completely supercedes wiping the image.
Your laptop being stolen after resume is very much a corner case.
You suspend your laptop while you are not around, don't you?

Additionally it helps only if you cannot trigger another swsusp, eg by
running dry the batteries.

	Regards
		Oliver
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