linux-kernel - Re: debugfs & vfs file permission issue?

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Message-ID: <8bd0f97a0901060720l40099bd6o63a692e5fdd3e098@mail.gmail.com>
Date:	Tue, 6 Jan 2009 10:20:54 -0500
From:	"Mike Frysinger" <vapier.adi@...il.com>
To:	"Robin Getz" <rgetz@...ckfin.uclinux.org>
Cc:	"Greg KH" <gregkh@...e.de>, viro@...iv.linux.org.uk,
	linux-kernel@...r.kernel.org
Subject: Re: debugfs & vfs file permission issue?

On Tue, Jan 6, 2009 at 10:12, Robin Getz wrote:
> On Tue 6 Jan 2009 07:05, Robin Getz suggested:
>> adding a readonly, and writeonly, and ensuring that when you call
>> debugfs_create_*, the mode is checked, and the "correct" fops are set
>> doesn't seem like it would be a bad idea? This would enforce the
>> kernel programmer's view on the world, and not allow pesky root users
>> to override things....
>>
>> Greg - would you take something like that?
>
> How about this?
>
> Feel free to nak it - we can do the same thing where we are calling the
> debugfs_create_* functions - this just makes it cleaner in my opinion.
>
> ---
>
> In many SOC implementations there are hardware registers can be read only,
> or write only. This extends the debugfs to enforce the file permissions for
> these types of registers, by providing a set of fops which are read only
> or write only. This assumes that the kernel developer knows more about the
> hardware than the user (even root users) - which is normally true.

we want it for cpu registers, but i dont see any reason why this
wouldnt also apply to external devices attached via memory interfaces
... fifos and such ...
-mike
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