linux-hardening - Re: [PATCH v3 3/4] string: Allow 2-argument strscpy

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Date: Wed, 7 Feb 2024 01:18:49 -0800
From: Kees Cook <keescook@...omium.org>
To: Justin Stitt <justinstitt@...gle.com>
Cc: Andy Shevchenko <andy@...nel.org>, linux-hardening@...r.kernel.org,
	Richard Weinberger <richard@....at>,
	Anton Ivanov <anton.ivanov@...bridgegreys.com>,
	Johannes Berg <johannes@...solutions.net>,
	Willem de Bruijn <willemdebruijn.kernel@...il.com>,
	Jason Wang <jasowang@...hat.com>, kernel test robot <lkp@...el.com>,
	Nathan Chancellor <nathan@...nel.org>,
	Azeem Shaikh <azeemshaikh38@...il.com>,
	linux-kernel@...r.kernel.org, linux-um@...ts.infradead.org
Subject: Re: [PATCH v3 3/4] string: Allow 2-argument strscpy_pad()

On Wed, Feb 07, 2024 at 12:51:51AM +0000, Justin Stitt wrote:
> Hi,
> 
> On Tue, Feb 06, 2024 at 06:22:18AM -0800, Kees Cook wrote:
> > Similar to strscpy(), update strscpy_pad()'s 3rd argument to be
> > optional when the destination is a compile-time known size array.
> 
> This patch is diff'd against Patch 1/4 in this series, right? I wonder
> why you split them up. If I hadn't literally just read that patch I
> would be mildly confused.
> 
> I suppose one reason may be that 1/4 is a standalone change with a high
> percentage chance of landing whilst this overloading magic may not land
> as easily?

I viewed it as a distinct logical change. I could certainly combine
them, but I think it's easier to review the conversion from function to
macro without needing to consider anything else. No behavioral changes
are expected, etc.

But if they were together, there's a little more cognitive load to keep
the func/macro conversion in mind while looking at the optional arg
magic, etc.

I don't think it's a strict rule or anything; it just felt like the
right thing to do to split them up.

> At any rate,
> Reviewed-by: Justin Stitt <justinstitt@...gle.com>

Thanks!

-Kees

-- 
Kees Cook