linux-kernel - Re: [PATCH] x86/microcode/AMD: Fix out-of-bounds on systems with CPU-less NUMA nodes

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Message-ID: <CABRcYmLcXosu62EbTMQNGCEa+mmNtRKCQX8oL=WDrgP-UH6B_g@mail.gmail.com>
Date: Fri, 7 Mar 2025 16:58:16 +0100
From: Florent Revest <revest@...omium.org>
To: Dave Hansen <dave.hansen@...el.com>
Cc: bp@...en8.de, linux-kernel@...r.kernel.org, tglx@...utronix.de, 
	mingo@...hat.com, dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com, 
	stable@...r.kernel.org
Subject: Re: [PATCH] x86/microcode/AMD: Fix out-of-bounds on systems with
 CPU-less NUMA nodes

On Fri, Mar 7, 2025 at 3:55 PM Dave Hansen <dave.hansen@...el.com> wrote:
>
> On 3/7/25 05:12, Florent Revest wrote:
> >       for_each_node(nid) {
> > -             cpu = cpumask_first(cpumask_of_node(nid));
> > +             mask = cpumask_of_node(nid);
> > +             if (cpumask_empty(mask))
> > +                     continue;
> > +
> > +             cpu = cpumask_first(mask);
>
> Would for_each_node_with_cpus() trim this down a bit?

Oh nice, I didn't notice this macro, thanks for pointing it out! :)
I'm happy to respin a v2 using for_each_node_with_cpus(), I'll just
leave a bit more time in case there are other comments.

One thing I'm not entirely sure about is that
for_each_node_with_cpus() is implemented on top of
for_each_online_node(). This differs from the current code which uses
for_each_node(). I can't tell if iterating over offline nodes is a bug
or a feature of load_microcode_amd() so this would be an extra change
to the business logic which I can't really explain/justify.