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Re: [PATCH RESEND 2/2] Fix some kallsyms_lookup() vs rmmod races [message #11306 is a reply to message #11268] Sat, 17 March 2007 09:37 Go to previous messageGo to previous message
Rusty Russell is currently offline  Rusty Russell
Messages: 10
Registered: March 2007
Junior Member
On Fri, 2007-03-16 at 12:51 +0100, Ingo Molnar wrote:
> * Alexey Dobriyan <adobriyan@sw.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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