linux-kernel - Re: [PATCH v3] vfs: new O

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Date:	Mon, 7 Dec 2009 12:23:46 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	miklos@...redi.hu, luto@....edu, akpm@...ux-foundation.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] vfs: new O_NODE open flag

The standard udev unload is a true open barrier so has an implicit
revoke() caused by the fact you cannot keep a handle to the filename open
during the udev sequence (or the old driver would be pinned by a refcount
and not unload).

This isn't about hard links, its about object and handle lifetimes.
Ownership is also involved in the case of things like a tty device (so if
you can fchmod down the handle you can break the security model).

It only works because you have a true revoke (by virtue of refcounting in
the kernel driver modules)

Alan
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