linux-kernel - Re: NULL pointer dereference in sysfs

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Message-Id: <200610221240.42061.mb@bu3sch.de>
Date:	Sun, 22 Oct 2006 12:40:41 +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,
	Dave Jones <davej@...hat.com>
Subject: Re: NULL pointer dereference in sysfs_readdir

On Sunday 22 October 2006 11:08, Stefan Richter wrote:
> > 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.
> 
> What if "next" became NULL afterwards?

Hm, yeah. Makes kind of sense.

> I know it's unlikely (but so is 
> the whole bug, given that we have just one reporter despite the bug's
> age), but is it impossible? IOW does sysfs_readdir have any indirect
> mutex protection?

I think it's protected by the BKL, but I dunno if that's sufficient here.

-- 
Greetings Michael.
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