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SubjectRe: ide-cd problems
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.

>
> > * You can't open the device unless there is media in the drive
>
> False, you use O_NONBLOCK.

Thanks, I didn't know about this one -- works great :)


>
[snip stuff about scatter gather/manual dma]
>
> --
> Jens Axboe

--
Zinx Verituse http://zinx.xmms.org/
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