Re: [security]: kernel ioctl()'s

Chris Evans (chris@ferret.lmh.ox.ac.uk)
Fri, 2 Jul 1999 00:56:02 +0100 (GMT)


On Fri, 2 Jul 1999, Jamie Lokier wrote:

> > Is FIBMAP used by anything? It would seem to me to be offering users
> > read access to internal filesystem structures - and as such should be
> > restricted to root (CAP_SYS_ADMIN or something).
>
> FIBMAP is used by bootloaders.

.. which run as root so restriction won't break those.

> It can also be used to optimise file access at the user level --
> arguably a dubious thing to do, I'll get back to you when I've done the

Conceptually, I don't like offering a "backdoor" to internal storage
layout/format. If there's a filesystem load pattern for which we are
suboptimal, the solution should be to educate the kernel rather than
exposing internal details of file layout to userland.

Chris

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