linux-ext4 - Re: Bug#692104: linux-image-3.2.0-3-amd64: NULL pointer dereference in ext4fs

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Message-ID: <509C3156.6090500@gaast.net>
Date:	Thu, 08 Nov 2012 22:25:26 +0000
From:	Wilmer van der Gaast <wilmer@...st.net>
To:	Theodore Ts'o <tytso@....edu>
CC:	Ben Hutchings <ben@...adent.org.uk>, linux-ext4@...r.kernel.org,
	692104@...s.debian.org
Subject: Re: Bug#692104: linux-image-3.2.0-3-amd64: NULL pointer dereference
  in ext4fs

Hello all,

This crash has happened to me three times now, but the last time is is 
five days ago. Seems to have disappeared as mysteriously as it appeared.

On 08-11-12 15:30, Theodore Ts'o wrote:
> On Fri, Nov 02, 2012 at 10:52:35PM +0100, Wilmer van der Gaast wrote:
>> whether my filesystem is corrupted. I'll make an LVM snapshot and
>> then do a full fsck.
>
That fsck was completely clean by the way.

> Did you perform another on-line resize on the file system before it
> failed?
>
I don't think so. I've done one last weekend, after which I've 
experienced one more crash. I'm quite sure that the last on-line resize 
before I reported this bug is quite long ago though, likely before my 
last reboot.

> It looks like a problem which I ran into (and fixed) when adding
> support for online resizing for>  16TB file systems, [...]

The filesystem is not quite that large, just 45G (from 40G).

I've attached tune2fs output for it just in case it helps. It was 
created back in 2010 already apparently, although as an ext3 at the time.

> you resize it?  If it is this bug, the s_group_info array is allocated
> based on the file system size when the file system is mounted.  So it
> would only be happening after a online resize and before the file
> system is unmounted and/or the system is rebooted and the file system
> is mounted again.
>
Hmm, I'm quite sure a long time (and likely a reboot) had passed in 
between the last resize and the first crash last weekend.

It looked like this crash always happened while handling a close() 
syscall issued by Firefox. I've tried stracing my firefox process to see 
which file was causing it, but the crashes had already disappeared by then.

I'll definitely ping this bug if this happens again.


Thanks,

Wilmer v/d Gaast.

-- 
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| wilmer : :'  :  gaast.net |  | OSS Programmer   www.bitlbee.org |
| lintux `. `~'  debian.org |  | Full-time geek  wilmer.gaast.net |
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View attachment "tune2fs.txt" of type "text/plain" (1735 bytes)