Re: [PATCH v3] vfs: new O_NODE open flag

[Alan Cox]

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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