Re: Direct access to hardware

Miquel van Smoorenburg (miquels@cistron.nl)
Sat, 22 Jul 2000 13:44:50 +0200

According to James Sutherland:
> On 21 Jul 2000, Miquel van Smoorenburg wrote:
> > It _is_ possible. Check out "capabilities".
>
> It isn't possible. Root can bypass them all completely, as long as
> /dev/kmem etc. exist.

If CAP_SYS_RAWIO isn't set, even root cannot open /dev/mem /dev/kmem
and /dev/port. Read linux/char/mem.c, check open_port etc

> Shall we delete capabilities on this basis? I think
> not - so why apply that argument to Andre's bugfix?

Well no, as many others have pointed out, it's the other way around-
capabilities should be applied to everything that gives access to
some hardware's firmware programming interface.

Mike.

-- 
Cistron Certified Internetwork Expert #1.


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