Re: "Fix ATAPI transfer lengths" causes CD writing regression

Jens Axboe
2007-10-31T17:55:57Z

On Wed, Oct 31 2007, Jeff Garzik wrote:
> Jens Axboe wrote:
> >Right, that's of course problematic... There has to be a way to recover
> >that situation though, or you can't export any user command issue
> >facility.
>
> You cannot hope to handle all possible effects arising from an app
> providing an invalid sg header / cdb.
>
> Once you start talking "recovery" you are already screwed: we are
> talking about low-level hardware commands that are passed straight to
> the hardware. It is trivial to lock up hardware, brick hardware, and
> corrupt data at that level.
>
>
> If this is NOT a privileged app, we must update the command validation
> to ensure that invalid commands are not transported to the hardware.
>
> If this is a privileged app, our work is done. Fix the app. We gave
> root rope, and he took it.

Woaw, back the truck up a bit :-)

I'm talking about simple things - like asking for 8 bytes of sense data.
Simple mistakes. You cannot possibly check for everything like that in a
command filter, it's utterly impossible.

> I even venture to say that "accept anything, clean up afterwards" is
> /impossible/ to implement, in addition to being dangerous.

Certainly, that's not what I'm talking about.

--
Jens Axboe