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Subject: Re: [PATCH RESEND 2/2] Fix some kallsyms_lookup() vs rmmod races
From: Rusty Russell <rusty@rustcorp.com.au>
To: Alexey Dobriyan <adobriyan@sw.ru>
Cc: akpm@osdl.org, linux-kernel@vger.kernel.org, devel@openvz.org,
       mingo@elte.hu, tglx@linutronix.de, viro@zeniv.linux.org.uk,
       pmarques@grupopie.com
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Date: Sat, 17 Mar 2007 20:32:51 +1100
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On Fri, 2007-03-16 at 14:44 +0300, Alexey Dobriyan 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:

Yes, this changed somewhere along the way. 

I prefer keeping the lock internal as much as possible, and have the
crash code use an __ variant of the function.

Note also that it might be an idea to have less-powerful accessors than
kallsyms_lookup...

Thanks!
Rusty.