linux-kernel - Re: cdrom: cdrom_mrw

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Message-ID: <aHbOR4IANvJWfG-L@equinox>
Date: Tue, 15 Jul 2025 22:55:19 +0100
From: Phillip Potter <phil@...lpotter.co.uk>
To: Sergey Senozhatsky <senozhatsky@...omium.org>
Cc: Jens Axboe <axboe@...nel.dk>, Phillip Potter <phil@...lpotter.co.uk>,
	Sergey Senozhatsky <senozhatsky@...omium.org>,
	Christoph Hellwig <hch@...radead.org>,
	Chris Rankin <rankincj@...il.com>, linux-kernel@...r.kernel.org,
	linux-block@...r.kernel.org
Subject: Re: cdrom: cdrom_mrw_exit() NULL ptr deref

On Tue, Jul 15, 2025 at 12:32:22PM +0900, Sergey Senozhatsky wrote:
> On (25/07/14 08:22), Jens Axboe wrote:
> > This just looks totally broken, the cdrom layer trying to issue block
> > layer commands at exit time. Perhaps something like the below (utterly
> > untested) patch would be an improvement. Also gets rid of the silly
> > ->exit() hook which exists just for mrw.
> 
> I don't have a CD/DVD drive to test this, but from what I can tell
> the patch looks good to me.  Thanks for taking a look!

So thus far I've not been able to reproduce this. I've just ordered some
more rewritable discs though, so once they arrive I will produce some
proper sample discs and attempt to get it to crash again.

I will also run Jens's patch too with one of these discs to verify things
continue to work (and indeed that it improves things in the event I can
reproduce, which I'm sure it would).

Regards,
Phil