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Re: cdrecord and newer Linux kernels



[ Bugger, got the cdrtools-devel address wrong on the first mail. Now
  fixed. ]

On Fri, Nov 11, 2005 at 12:53:00AM +0100, Christoph Hellwig wrote:
>On Thu, Nov 10, 2005 at 11:47:29PM +0000, Steve McIntyre wrote:
>> In kernel 2.6.8 and later, SCSI generic commands are verified for
>> safety. This may be a reasonable measure in some respects, but it
>> makes effective non-root CD/DVD burning rather difficult. For best
>> performance cdrecord, growisofs and friends may often need to send
>> SCSI commands to drives that the kernel may neither know about nor
>> understand. And (to add to the pain) these commands are very often
>> vendor- or device-specific, so simply allowing those commands in the
>> kernel will defeat the point of the verification in the first place.
>
>The whole point of the verification is to allow safe access to a
>selected set of raw commands for normal users.  root (or rather
>a process that has CAP_SYS_RAWIO) can send any command.  if you need
>unknown commands just make sure to burn as root, as everything else
>would be unsafe anyway.

That does make it rather difficult to have any safe CD/DVD writing
software - do you think it's a good idea to have end users run apps as
root to burn CDs? I've read too much of the cdrecord source to be
happy running that as root! :-) My thought is that it might be better
to allow specific commands on specific drives, and let the local admin
configure that for themselves...

-- 
Steve McIntyre, Cambridge, UK.                                steve@einval.com
Can't keep my eyes from the circling sky,
Tongue-tied & twisted, Just an earth-bound misfit, I...

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