On Sat, Mar 17, 2007 at 08:37:18PM +1100, Rusty Russell wrote: > On Fri, 2007-03-16 at 12:51 +0100, Ingo Molnar wrote: > > * Alexey Dobriyan <[EMAIL PROTECTED]> 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.
mmm, my changelog is slightly narrow than it should be. Non-emergency code is traversing modules list. It finds "struct module *". module is removed. "struct module *" is now meaningless, but still dereferenced. How would all this refrigerator stuff would help? It wouldn't, Non-emergency code is traversing modules list. It finds "struct module *". Everything is freezed. Module is removed. Everything is unfreezed. "struct module *" is now meaningless, but still dereferenced. > Alexey, is preempt enabled in your kernel? Yes. FWIW, CONFIG_PREEMPT=y CONFIG_PREEMPT_BKL=y CONFIG_DEBUG_PREEMPT=y I very much agree with proto-patch which _copies_ all relevant information into caller-supplied structure, keeping module_mutex private. Time to split it sanely. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/