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

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Date:	Sat, 16 Mar 2013 10:54:57 +0100
From:	Clemens Ladisch <clemens@...isch.de>
To:	Prarit Bhargava <prarit@...hat.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] hpet, allow user controlled mmap for user processes

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.

I'm not aware of any such system (but cannot rule out the possibility).

> 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.

This introduces a regression for all users.  At least make the default
state (allowed/forbidden) configurable.

Also, this patch makes the Kconfig help text a lie.


Regards,
Clemens
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