Re: silent semantic changes with reiser4

[Jamie Lokier]

Christoph Hellwig wrote:
>  you need to fstat after open to really check that no one swtiched the
>  path below you to a fifo or device, O_DIRECTORY gets that directly in
>  the open call, with the additional benefit of making sure you don't
>  get any of the sideeffects at all that would happen if you're opening
>  a device file.
> 
>  the current reiser4 semantics break that and as soon as you're having a
>  world-writeable (e.g. /tmp) dir on it and someone is doing an opendir
>  on it he's lost.

How does the current reiser4 semantics break that?

In a reiser4 filesystem, a file _is_ a directory.
opendir() is supposed to succeed on it.

There's bound to be some security issue, but I'm not sure what you're
getting at with /tmp.  What sort of sort of security problem arises
with a world-writeable directory such as /tmp, that cannot arise with
the standard fs semantics?

-- Jamie
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