CD-RW not recognized with new kernel
James Wilkinson
james at westexe.demon.co.uk
Sat Aug 21 12:15:38 UTC 2004
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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