linux-kernel - Re: [PATCH] Fix array overflow in CFQ

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Message-ID: <x49bp6n1n8o.fsf@segfault.boston.devel.redhat.com>
Date:	Thu, 21 Oct 2010 13:15:03 -0400
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Andi Kleen <ak@...ux.intel.com>
Cc:	Vivek Goyal <vgoyal@...hat.com>, Jens Axboe <axboe@...nel.dk>,
	Andi Kleen <andi@...stfloor.org>,
	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Fix array overflow in CFQ

Andi Kleen <ak@...ux.intel.com> writes:

>> > Agreed.
>> >
>> > Jens, do you want me to regenerate your patch so that we increase the
>> > size of ->busy_queues_avg[CFQ_PRIO_NR] but not ->service_trees[][].
>> 
>> Just be sure to put a huge comment in there so you don't confuse the
>> poor masses trying to make sense of the code.
>
> Right now the code is confusing, with a correctly sized array it would
> be completely straight forward.

That's not entirely true.  You want a comment to state that the array
size is adjusted to ensure no accidental overflows, but in reality, that
third bucket is never used.

Cheers,
Jeff
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