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SubjectRe: ide-cd problems
On Sat, Jul 31 2004, Zinx Verituse wrote:
> On Sat, Jul 31, 2004 at 05:36:10PM +0200, Jens Axboe wrote:
> > On Fri, Jul 30 2004, Zinx Verituse wrote:
> > > I'm going to bump this topic a bit, since it's been a while..
> > > There are still some issues with ide-cd's SG_IO, listed from
> > > most important as percieved by me to least:
> > >
> > > * Read-only access grants you the ability to write/blank media in the drive
> > > * (with above) You can open the device only in read-only mode.
> >
> > That's by design. Search linux-scsi or this list for why that is so.
>
> The only thing I can find on the linux-scsi list is refering to sg
> devices, which are on a different device node from the non-generic
> device. This means you can still allow users read access to the disk
> without allowing them to send random commands to the disk -- this isn't
> currently possible with the IDE interface, since the device with
> generic access is the same as the one with the original read/cdrom
> commands access.
>
> As it is, it's impossible grant users read-only access to an IDE cd-rom
> without allowing them to do things like replacing the firmware with a
> malicious/non-working one.
>
> Generic access allowing such things is fine; but only if we can grant
> non-generic access without granting generic access.

If you want it to work that way, you have the have a pass-through filter
in the kernel knowing what commands are out there (including vendor
specific ones). That's just too ugly and not really doable or
maintainable, sorry.

If you have access to issue ioctls to the device, you have access to
send it arbitrary commands - period.

--
Jens Axboe

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