linux-kernel - Re: NULL pointer dereference in sysfs

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Message-ID: <45470B23.6070901@s5r6.in-berlin.de>
Date:	Tue, 31 Oct 2006 09:36:51 +0100
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	maneesh@...ibm.com
CC:	linux-kernel@...r.kernel.org, Greg KH <gregkh@...e.de>
Subject: Re: NULL pointer dereference in sysfs_readdir

Maneesh Soni wrote on 2006-10-30:
> On Sat, Oct 21, 2006 at 10:43:49AM +0200, Stefan Richter wrote:
...
>> A quick look at linux-2.6.19-rc2/fs/sysfs/dir.c::sysfs_readdir shows a
>> list_move, a traversal through a list, and some accesses to data with no
>> apparent protection by mutexes.
>>
> Most of the sysfs locking is done by parent inode's i_mutex. And for
> sysfs_readdir(), i_mutex is held at VFS layer in vfs_readdir().

OK, thanks.

> If this is not happening during boot, could you please recreate the
> oops with at kdump? I guess kdump should work well on FC.

The report came from someone else; I notified him. I cannot reproduce
it, I don't have FC nor hald. BTW the reporter mentioned that the
machine freezes completely much more often than merely throwing an oops.
(Both caused by hald.)

> (http://fedoraproject.org/wiki/FC6KdumpKexecHowTo?highlight=%28FC6KdumpKexecHowTo%29)
> 
>> Is there reason to be worried...?
> 
> Though locking looks fine to me.. but oops is a reason enough to
> be worried about.

I referred to the locking. :-) Thanks for the hints,
-- 
Stefan Richter
-=====-=-==- =-=- =====
http://arcgraph.de/sr/
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