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Re: [PATCH] cfg80211: fix race condition with wiphy_apply_custom_regulatory()

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On 5/4/09, Luis R. Rodriguez <lrodriguez@xxxxxxxxxxx> wrote:
> On Sat, May 02, 2009 at 07:29:43AM -0700, Alan Jenkins wrote:
>> On 5/1/09, Luis R. Rodriguez <lrodriguez@xxxxxxxxxxx> wrote:
>> > We forgot to lock using the cfg80211_mutex in
>> > wiphy_apply_custom_regulatory(). Without the lock
>> > there is possible race between processing a reply from CRDA
>> > and a driver calling wiphy_apply_custom_regulatory(). During
>> > the processing of the reply from CRDA we free last_request and
>> > wiphy_apply_custom_regulatory() eventually accesses an
>> > element from last_request in the through freq_reg_info_regd().
>> >
>> > This is very difficult to reproduce (I haven't), it takes us
>> > 3 hours and you need to be banging hard, but the race is obvious
>> > by looking at the code.
>> >
>> > This should only affect those who use this caller, which currently
>> > is ath5k, ath9k, and ar9170.
>> >
>> > EIP: 0060:[<f8ebec50>] EFLAGS: 00210282 CPU: 1
>> > EIP is at freq_reg_info_regd+0x24/0x121 [cfg80211]
>>
>> This looks like the same bug I reported seeing on bootup (100% of the
>> time).  I'll test wireless-testing again for V9 of the rfkill rewrite,
>> so at that point I'll try to confirm that this patch fixes my problem.
>
> Any luck?

Ugh, sorry, I can't reproduce it to test the patch.

I reported that it went away after making CFG80211 built-in, but I
can't get it back now, even if I turn that back into a module.  Maybe
I overwrote the original config, or maybe I was being dumb and it only
happened once in the first place.  I'm confident I'm using the same
source code (v2.6.30-rc2-21665-gca0be26, clean tree), so that's not
it.
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