linux-kernel - Re: BUG: Null pointer dereference in fs/open.c

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Message-ID: <Pine.LNX.4.64.0704260029400.25153@server.thyself>
Date:	Thu, 26 Apr 2007 00:48:35 +0000 (GMT)
From:	William Heimbigner <icxcnika@....tar.cc>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	linux-kernel@...r.kernel.org, Jens Axboe <jens.axboe@...cle.com>,
	Christoph Hellwig <hch@....de>, linux-ide@...r.kernel.org
Subject: Re: BUG: Null pointer dereference in fs/open.c

On Wed, 25 Apr 2007, Andrew Morton wrote:
> On Wed, 25 Apr 2007 22:53:00 +0000 (GMT) William Heimbigner <icxcnika@....tar.cc> wrote:
>
>> On Wed, 25 Apr 2007, Andrew Morton wrote:
>> <snip>
>>> OK.  I am able to use the pktcdvd driver OK in mainline with a piix/sata
>>> drive.  It could be that something is going wrong at the IDE level for you.
>> Perhaps; I'll try an external usb cd burner, and see where that goes.
>>
>>> Are you able to identify the most recent kernel which actually worked?
>> No, because I haven't set packet writing up in Linux before - however, I do know
>> that I've successfully set up packet writing (using 2 of the 3 cd burners I
>> have) in another operating system before. I'll try 2.6.18 and see if that gets
>> me anywhere different, though.
>
> OK.
>
> A quick summary: mainline's pktcdvd isn't working for William using IDE.
> It is working for me using sata.
>
<snip>
>
> So what has happened here is that this code, in ide-cd.c's
> cdrom_decode_status() is now triggering:
>
> 	} else if (blk_pc_request(rq) || rq->cmd_type == REQ_TYPE_ATA_PC) {
> 		/* All other functions, except for READ. */
> 		unsigned long flags;
>
> 		/*
> 		 * if we have an error, pass back CHECK_CONDITION as the
> 		 * scsi status byte
> 		 */
> 		if (blk_pc_request(rq) && !rq->errors)
> 			rq->errors = SAM_STAT_CHECK_CONDITION;
>
>
> I suspect this is a bug introduced by
> 406c9b605cbc45151c03ac9a3f95e9acf050808c (in which case it'll be the third
> bug so far).
>
> Perhaps the IDE driver was previously not considering these requests to be
> of type blk_pc_request(), and after
> 406c9b605cbc45151c03ac9a3f95e9acf050808c it _is_ treating them as
> blk_pc_request() and is incorrectly reporting an error.  Or something like
> that.
>
> Guys: help!
>
A follow-up: after looking around a bit, I have managed to get packet writing to 
work properly on /dev/hdc (before, it was reporting only 1.8 MB available or so; 
this was a formatting issue).
I've also gotten the external cd-rw drive to work. However, I'm still at a loss 
as to why /dev/hdd won't work. I tried formatting a dvd-rw for this drive, 
however, it consistently gives me:
[27342.503933] drivers/ide/ide-cd.c:729: setting error to 2
[27342.509251]  [<c010521a>] show_trace_log_lvl+0x1a/0x30
[27342.514411]  [<c0105952>] show_trace+0x12/0x20
[27342.518864]  [<c0105a46>] dump_stack+0x16/0x20
[27342.523317]  [<c033f6e4>] cdrom_decode_status+0x1f4/0x3b0
[27342.528732]  [<c033fae8>] cdrom_newpc_intr+0x38/0x320
[27342.533791]  [<c0331106>] ide_intr+0x96/0x200
[27342.538157]  [<c0150cf8>] handle_IRQ_event+0x28/0x60
[27342.543139]  [<c0151f96>] handle_edge_irq+0xa6/0x130
[27342.548121]  [<c0106449>] do_IRQ+0x49/0xa0
[27342.552228]  [<c0104c3a>] common_interrupt+0x2e/0x34
[27342.557200]  [<c01022d2>] mwait_idle+0x12/0x20
[27342.561653]  [<c01023ca>] cpu_idle+0x4a/0x80
[27342.565934]  [<c0101147>] rest_init+0x37/0x40
[27342.570300]  [<c068ac7b>] start_kernel+0x34b/0x420
[27342.575109]  [<00000000>] 0x0
[27342.578089]  =======================
and doesn't work (the above output was generated by Andrew's patch to log 
certain areas).

# dvd+rw-format /dev/hdd -force
* BD/DVDRW/-RAM format utility by <appro@...chalmers.se>, version 7.0.
:-( failed to locate "Quick Format" descriptor.
* 4.7GB DVD-RW media in Sequential mode detected.
* formatting 0.0\:-[ READ TRACK INFORMATION failed with SK=3h/ASC=11h/ACQ=05h]: Input/output error

I tried putting in a different dvd-rw, and this time I get:
# dvd+rw-format /dev/hdd -force
* BD/DVDRW/-RAM format utility by <appro@...chalmers.se>, version 7.0.
* 4.7GB DVD-RW media in Sequential mode detected.
* formatting 0.0|:-[ FORMAT UNIT failed with SK=5h/ASC=26h/ACQ=00h]: Input/output error

William Heimbigner
icxcnika@....tar.cc
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