linux-kernel - Re: [PATCH RESEND 2/2] Fix some kallsyms

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Message-Id: <1174124239.8897.41.camel@localhost.localdomain>
Date:	Sat, 17 Mar 2007 20:37:18 +1100
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Alexey Dobriyan <adobriyan@...ru>, akpm@...l.org,
	linux-kernel@...r.kernel.org, devel@...nvz.org, tglx@...utronix.de,
	viro@...iv.linux.org.uk, pmarques@...popie.com
Subject: Re: [PATCH RESEND 2/2] Fix some kallsyms_lookup() vs rmmod races

On Fri, 2007-03-16 at 12:51 +0100, Ingo Molnar wrote:
> * Alexey Dobriyan <adobriyan@...ru> wrote:
> 
> > [cc'ing folks whose proc files are affected]
> > 
> > kallsyms_lookup() can call module_address_lookup() which iterates over 
> > modules list without module_mutex taken. Comment at the top of 
> > module_address_lookup() says it's for oops resolution so races are 
> > irrelevant, but in some cases it's reachable from regular code:
> 
> looking at the problem from another angle: wouldnt this be something 
> that would benefit from freeze_processes()/unfreeze_processes(), and 
> hence no locking would be required?

Actually, the list manipulation is done with stop_machine for this
reason. Alexey, is preempt enabled in your kernel?

Rusty.


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