linux-kernel - Re: NULL pointer dereference in sysfs

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Message-Id: <200610212325.18976.mb@bu3sch.de>
Date:	Sat, 21 Oct 2006 23:25:18 +0200
From:	Michael Buesch <mb@...sch.de>
To:	Stefan Richter <stefanr@...6.in-berlin.de>
Cc:	Greg KH <gregkh@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: NULL pointer dereference in sysfs_readdir

On Saturday 21 October 2006 23:09, Stefan Richter wrote:
> Michael Buesch wrote:
> > On Saturday 21 October 2006 10:43, Stefan Richter wrote:
> ...
> >> https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=188140
> ...
> > Looking through the code I was not able to locate the exact line
> > at which it oopses, with the above oops message.
> > Are you able to track down the exact pointer dereference, which causes
> > this? By inserting printks, perhaps.
> 
> I need the original reporter to do this since I cannot reproduce the
> bug. Probably because I don't have an SMP machine yet.
> 
> > Maybe FC changed some of the structures. I couldn't find
> > a used structure with an interresting member at offset 00000020, at least.
> 
> Could be struct sysfs_dirent.s_dentry if I'm counting correctly in
> http://www.linux-m32r.org/lxr/http/source/include/linux/sysfs.h?v=2.6.16#L68
> The trace was from 2.6.16.

Yeah, I found that offset, too, but:

There is only one usage of s_dentry
if (next->s_dentry)

But _before_ that there already comes
if (!next->s_element)

So, if "next" was NULL, it would already oops there.

-- 
Greetings Michael.
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