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

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Date:	Tue, 19 Mar 2013 08:43:25 +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.
>
> 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.
>
> Signed-off-by: Prarit Bhargava <prarit@...hat.com>
> Cc: Clemens Ladisch <clemens@...isch.de>

> +++ b/Documentation/kernel-parameters.txt
> +	hpet_mmap_enable [X86, HPET_MMAP] option to expose HPET MMAP to
> +			 userspace.  By default this is disabled.

This now takes a value.

> +	int "Enable HPET MMAP access by default"
> +	range 0 1

Shouldn't this be bool?

> +	default 0

This breaks backwards compatibility.


Regards,
Clemens
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