linux-kernel - Re: [PATCH] hpet, allow user controlled mmap for user processes

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Message-ID: <20130829060151.GA7439@u109add4315675089e695.ant.amazon.com>
Date:	Wed, 28 Aug 2013 23:01:53 -0700
From:	Matt Wilson <msw@...zon.com>
To:	Prarit Bhargava <prarit@...hat.com>
CC:	<linux-kernel@...r.kernel.org>,
	Clemens Ladisch <clemens@...isch.de>
Subject: Re: [PATCH] hpet, allow user controlled mmap for user processes

On Fri, Mar 22, 2013 at 09:32:54AM -0400, Prarit Bhargava wrote:
> The CONFIG_HPET_MMAP Kconfig option exposes the memory map of the HPET
> registers to userspace.  The Kconfig help points out that in some cases this
> can be a security risk as some systems may erroneously configure the map such
> that additional data is exposed to userspace.
> 
> This is a problem for distributions -- some users want the MMAP functionality
> but it comes with a significant security risk.  In an effort to mitigate this
> risk, and due to the low number of users of the MMAP functionality, I've
> introduced a kernel parameter, hpet_mmap_enable, that is required in order
> to actually have the HPET MMAP exposed.
> 
> [v2]: Clemens suggested modifying the Kconfig help text and making the
> default setting configurable.
> [v3]: Fixed up Documentation and Kconfig entries, default now "Y"
> [v4]: After testing, found that I need to modify CONFIG_HPET_MMAP_DEFAULT usage
> 
> Signed-off-by: Prarit Bhargava <prarit@...hat.com>
> Cc: Clemens Ladisch <clemens@...isch.de>
> ---
>  Documentation/kernel-parameters.txt |    4 ++++
>  drivers/char/Kconfig                |    9 +++++++--
>  drivers/char/hpet.c                 |   25 +++++++++++++++++++++++--
>  3 files changed, 34 insertions(+), 4 deletions(-)

It doesn't seem like this patch got picked up and seems like a good
idea to me. Clemens, what do you think?

Acked-by: Matt Wilson <msw@...zon.com>

--msw
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