linux-hardening - Re: [PATCH v2 2/4] string: Allow 2-argument strscpy()

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Message-ID: <CAMuHMdXYri0tkVDORL468hc7_AXx4qnrT6wjKO69FpujbEehUQ@mail.gmail.com>
Date: Mon, 5 Feb 2024 14:07:56 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Kees Cook <keescook@...omium.org>
Cc: Andy Shevchenko <andy@...nel.org>, Justin Stitt <justinstitt@...gle.com>, 
	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 v2 2/4] string: Allow 2-argument strscpy()

Hi Kees,

On Mon, Feb 5, 2024 at 2:01 PM Kees Cook <keescook@...omium.org> wrote:
> On Mon, Feb 05, 2024 at 01:47:08PM +0100, Geert Uytterhoeven wrote:
> > > +/*
> > > + * The 2 argument style can only be used when dst is an array with a
> > > + * known size.
> > > + */
> > > +#define __strscpy0(dst, src, ...)      \
> > > +       sized_strscpy(dst, src, sizeof(dst) + __must_be_array(dst))
> > > +#define __strscpy1(dst, src, size)     sized_strscpy(dst, src, size)
> >
> > (dst), (src), (size) etc.
>
> I normally don't do this when macro args are being expanded into
> function arguments. I've only done it for when macro args are used in
> expressions. Am I missing a side-effect here, or is this more about
> stylistic consistency?

I'm not 100% sure it is needed, but I'm always wary when using macro
parameters without parentheses, except in the most simple use-cases.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds