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Date: Tue, 12 Mar 2013 09:06:36 -0400
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Subject: Re: security: restricting access to swap
Message-ID: <20130312130636.GC17901@phenom.dumpdata.com>
References: <CAA25o9RchY2AD8U30bh4H+fz6kq8bs98SUrkJUkTpbTHSGjcGA@mail.gmail.com>
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To: Luigi Semenzato <semenzato@google.com>
Cc: linux-mm@kvack.org

On Mon, Mar 11, 2013 at 04:57:25PM -0700, Luigi Semenzato wrote:
> Greetings linux-mmers,
> 
> before we can fully deploy zram, we must ensure it conforms to the
> Chrome OS security requirements.  In particular, we do not want to
> allow user space to read/write the swap device---not even root-owned
> processes.
> 
> A similar restriction is available for /dev/mem under CONFIG_STRICT_DEVMEM.
> 
> There are a few possible approaches to this, but before we go ahead
> I'd like to ask if anything has happened or is planned in this
> direction.
> 
> Otherwise, one idea I am playing with is to add a CONFIG_STRICT_SWAP
> option that would do this for any swap device (i.e. not specific to
> zram) and possibly also when swapping to a file.  We would add an
> "internal" open flag, O_KERN_SWAP, as well as clean up a little bit
> the FMODE_NONOTIFY confusion by adding the kernel flag O_KERN_NONOTIFY
> and formalizing the sets of external (O_*) and internal (O_KERN_*)
> open flags.
> 
> Swapon() and swapoff() would use O_KERN_SWAP internally, and a device
> opened with that flag would reject user-level opens.

What/who does the swapon/swapoff calls? Is there an kernel level thread
(aka init but in kernel?) that would do this?

> 
> Thank you in advance for any input/suggestion!
> Luigi
> 
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