linux-hardening - Re: [PATCH] thermal: core: Move initial num

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Date: Wed, 28 Feb 2024 09:56:51 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: Lukasz Luba <lukasz.luba@....com>
Cc: Kees Cook <keescook@...omium.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>, rui.zhang@...el.com,
	gustavoars@...nel.org, morbo@...gle.com, justinstitt@...gle.com,
	stanislaw.gruszka@...ux.intel.com, linux-pm@...r.kernel.org,
	linux-hardening@...r.kernel.org, llvm@...ts.linux.dev,
	patches@...ts.linux.dev, Daniel Lezcano <daniel.lezcano@...aro.org>
Subject: Re: [PATCH] thermal: core: Move initial num_trips assignment before
 memcpy()

On Wed, Feb 28, 2024 at 08:41:07AM +0000, Lukasz Luba wrote:
> Hi Nathan and Kees,
> 
> On 2/27/24 17:00, Kees Cook wrote:
> > On Tue, Feb 27, 2024 at 05:47:44PM +0100, Daniel Lezcano wrote:
> > > Ok my misunderstanding was I thought sizeof() was calling _bdos under the
> > > hood, so when calling sizeof(flex_array), it was returning the computed size
> > > inferring from the __counted_by field.
> > 
> > Yeah, sizeof() has a very limited scope. __builtin_object_size() has
> > more flexibility (via the 2nd argument, "type"), but it was still
> > compile-time only. __builtin_dynamic_object_size() was added to bring
> > runtime evaluations into the mix (initially to support the alloc_size
> > attribute, and now includes the counted_by attribute too).
> > 
> 
> Thanks for your earlier emails explaining these stuff.
> Do you have maybe some presentation about those features
> for the kernel (ideally w/ a video from some conference)?

I think Kees's 2022 and 2023 talks at LPC are a good place to start:

https://youtu.be/tQwv79i02ks?si=Nj9hpvmQwPB4K3Y4&t=452
https://youtu.be/OEFFqhP5sts?si=u6RnOP641S8FkouD&t=614

https://outflux.net/slides/2022/lpc/features.pdf
https://outflux.net/slides/2023/lpc/features.pdf

Cheers,
Nathan