linux-hardening - Re: [PATCH v3] sched/core: Address classes via __begin_sched

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Date:   Tue, 17 May 2022 10:35:44 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Christophe de Dinechin <dinechin@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v3] sched/core: Address classes via __begin_sched_classes

On Tue, May 17, 2022 at 01:46:54PM +0200, Peter Zijlstra wrote:
> On Mon, May 16, 2022 at 08:33:25PM -0700, Kees Cook wrote:
> 
> > I just need to start today over.
> 
> :-)
> 
> Also, even with this sorted, there's a ton array bound things left.
> Please don't just mangle the code until it stops complaining like in the
> previous postings of these patches.

Yeah, other code is much simpler. The sched code has been a bit tricky
to figure out.

> As such, I'm only barely ok with the below patch. Ideally I'd shoot GCC
> in the head. Its *really* tedious you cannot just tell it to shut up
> already.

What you've got below is almost exactly what I had in my first attempt
at this (that I never posted). What I was missing and couldn't track
down were the places you used sched_class_above(). I should have sent
_that_ patch and asked where the comparisons were that I couldn't find.
I think what you've got is much cleaner, as it makes the for loop use
the normal iterator idiom.

Thank you!

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook