linux-kernel - Re: get_device

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Message-ID: <4ACA9A20.4050809@kernel.org>
Date:	Tue, 06 Oct 2009 10:15:12 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Greg KH <greg@...ah.com>
CC:	Colin Guthrie <cguthrie@...driva.org>,
	Kay Sievers <kay.sievers@...y.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: get_device_parent() race bug

Greg KH wrote:
>>>  BUG: unable to handle kernel NULL pointer dereference at 0000000000000038
>> Ping.  This one needs to be fixed in -stable.  It can be triggered by
>> other char devices too.
>
> Sorry, been slowly catching up...
> 
> This can be triggered by char devices?  Huh?  How?  I don't see the
> failure path that is happening here.

Oooh, s/char/virtual/.  The bug is in the path which creates a
directory under the phony parent.

> And char devices shouldn't really be using the kobject at all, except
> for a very basic reference count.
> 
> I keep threatening to rip kobject out of a char device and just use a
> kref, as that is all that is really needed.  Well, that and the kmap
> stuff, but again, it's not a "real" kobject being used there...
> 
> Perhaps now is the time to do this.

Yay!

-- 
tejun
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