linux-kernel - Re: Why is FIBMAP ioctl root only?

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Message-ID: <20071122102951.24e4e781@laptopd505.fenrus.org>
Date:	Thu, 22 Nov 2007 10:29:51 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	Jan Kara <jack@...e.cz>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Why is FIBMAP ioctl root only?

On Thu, 22 Nov 2007 19:17:14 +0100
Jan Kara <jack@...e.cz> wrote:

>   Hi,
> 
>   I guess subject says it all - why is FIBMAP ioctl restricted only to
> root (CAP_SYS_RAWIO)? Corresponding ioctl for XFS is allowed without
> any special capabilities so we are inconsistent here too...
>   Would anyone mind if the check is removed?

probably principle of least privilege; the location on physical media
for a file is clearly something internal to the OS, and non-trusted
users normally don't have any business knowing that. 

I can't think of any immediate exploitable thing with it, but I'm sure
attackers would find a way to use it to increase their privilege once
they can do something like "write 512 bytes to a disk address of my
choice".. (but then again it's game over mostly already)

> 
> 								Honza

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