linux-kernel - Re: check capabilities in open()

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Message-ID: <20100726165235.GA3485@albatros>
Date:	Mon, 26 Jul 2010 20:52:35 +0400
From:	Vasiliy Kulikov <segooon@...il.com>
To:	Ted Ts'o <tytso@....edu>, Al Viro <viro@...IV.linux.org.uk>,
	kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: check capabilities in open()

On Mon, Jul 26, 2010 at 07:23 -0400, Ted Ts'o wrote:
> The reason why the apm device needed to sample the suser() bit is that
> it can be opened by root and non-root processes, but it wanted to
> extend the Unix/Linux paradigm that privileges are tested at open()
> time.
Yes, it's exactly that I mean, check at open() time and grand high or
less priviledges.

> 
> So this is a not a bug, but quite deliberately, by design.
If it is explicitly designed to check UID at open() time and to have 2
kinds of file descriptors - priviledged and nonpriviledged, I'm fine
with this.

I wanted kernel community to draw attention because this moment was
not obviously for me and I thought it was a design flaw. Now I'm pleased
with your explanation, thank you.
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