Re: CD-RW not recognized with new kernel

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Markus Huber wrote:
> Just installed the kernel#2.6.8-1.521, and the CD-RW is not recognized 
> as CD-Writer anymore. Under kernel#2.6.7-1.494.2.2 it still works 
> perfectly. I wonder if anybody else experiences that problem.
> 
> Here some useful (?) details & logs:
> 
> The device is listed in the hardwarebrowser as
> ATAPI CD-RW 52x24
> Device: /dev/hdc
> 
> That's perfect, at least it was.
> 
> The log for "nautilus --no-desktop burn:" is:
> 
> cdrecord: Illegal write mode for this drive.
> cdrecord: Drive does not support TAO recording.
> SCSI buffer size: 64512
> cdrecord: Warning: using inofficial libscg transport code version 
> (schily - Red Hat-scsi-linux-sg.c-1.80-RH '@(#)scsi-linux-sg.c    1.80 
> 04/03/08 Copyright 1997 J. Schilling').
> Linux sg driver version: 3.5.27
> Warning: Open by 'devname' is unintentional and not supported.
> scsibus: -2 target: -2 lun: -2
> devname: '/dev/hdc'
> scsidev: '/dev/hdc'
> cdrecord: WARNING: This causes a high risk for buffer underruns.
> cdrecord: Permission denied. WARNING: Cannot set priority using 
> setpriority().
> cdrecord: Operation not permitted. WARNING: Cannot set RR-scheduler
> cdrecord: WARNING: This causes a high risk for buffer underruns.
> cdrecord: Cannot allocate memory. WARNING: Cannot do mlockall(2).
> cdrecord: Continuing in 5 seconds...
> cdrecord: Future versions of cdrecord may have different drive dependent 
> defaults.
> cdrecord: Asuming -tao mode.
> cdrecord: No write mode specified.
> 
> I do not have a clue, because it happens just with this kernel, and I 
> don't find any information about that problem with the 2.6.8-kernel 
> through google.

If anyone has a LWN subscription, try looking at
http://lwn.net/Articles/98379/ for a good summary of the situation.

Brief workaround: run your CD recording program from a root shell, or
use sudo.

The problem is that CD recording needs some pretty low-level commands
to run. In
http://groups.google.com/groups?dq=&hl=en&lr=&ie=UTF-8&threadm=2tY9w-713-39%40gated-at.bofh.it&prev=/groups%3Fdq%3D%26num%3D100%26hl%3Den%26lr%3D%26ie%3DUTF-8%26group%3Dlinux.kernel%26start%3D400
(sorry about the length of that!), Alan Cox explains

> With the current code I can destroy all your hard disks given read
> access to the drive. With checks on writable I can destroy all your hard
> disks/cdroms as appropriate with write access.
>
> Destroy here means "dead, defunct, pushing up the daisies, go order
> a new one kind of dead".

It's considered that being able to do this as a non-root user is a
security bug. Better, more complex workarounds are being worked on: it's
likely that we're going to see cd writing special cased, and only the
commands needed for that allowed through.

James.

-- 
E-mail address: james | Never ask, "Oh, why were things so much better
@westexe.demon.co.uk  | in the old days?"
                      | It's not an intelligent question.
                      |     -- Ecclesiastes 7 v. 10



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