linux-kernel - Re: [PATCH] vsprintf: Use %p4chR instead of %p4cn for reading data in reversed host ordering

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAMuHMdX07EUSL2q5=jD17NX0gRMuLcWNec6i_18_vdnk5iC0bg@mail.gmail.com>
Date: Mon, 28 Apr 2025 15:33:26 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Petr Mladek <pmladek@...e.com>
Cc: alyssa@...enzweig.io, Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, 
	Sven Peter <sven@...npeter.dev>, Thomas Zimmermann <tzimmermann@...e.de>, 
	Aun-Ali Zaidi <admin@...eit.net>, Maxime Ripard <mripard@...nel.org>, airlied@...hat.com, 
	Simona Vetter <simona@...ll.ch>, Steven Rostedt <rostedt@...dmis.org>, 
	Rasmus Villemoes <linux@...musvillemoes.dk>, Sergey Senozhatsky <senozhatsky@...omium.org>, 
	Jonathan Corbet <corbet@....net>, Andrew Morton <akpm@...ux-foundation.org>, apw@...onical.com, 
	joe@...ches.com, dwaipayanray1@...il.com, lukas.bulwahn@...il.com, 
	Kees Cook <kees@...nel.org>, tamird@...il.com, Aditya Garg <gargaditya08@...e.com>, 
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, dri-devel@...ts.freedesktop.org, 
	linux-doc@...r.kernel.org, Hector Martin <marcan@...can.st>, 
	Asahi Linux Mailing List <asahi@...ts.linux.dev>
Subject: Re: [PATCH] vsprintf: Use %p4chR instead of %p4cn for reading data in
 reversed host ordering

On Mon, 28 Apr 2025 at 14:31, Petr Mladek <pmladek@...e.com> wrote:
> The generic FourCC format always prints the data using the big endian
> order. It is generic because it allows to read the data using a custom
> ordering.
>
> The current code uses "n" for reading data in the reverse host ordering.
> It makes the 4 variants [hnbl] consistent with the generic printing
> of IPv4 addresses.
>
> Unfortunately, it creates confusion on big endian systems. For example,
> it shows the data &(u32)0x67503030 as
>
>         %p4cn   00Pg (0x30305067)
>
> But people expect that the ordering stays the same. The network ordering
> is a big-endian ordering.
>
> The problem is that the semantic is not the same. The modifiers affect
> the output ordering of IPv4 addresses while they affect the reading order
> in case of FourCC code.
>
> Avoid the confusion by replacing the "n" modifier with "hR", aka
> reverse host ordering. It is inspired by the existing %p[mM]R printf
> format.
>
> Reported-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> Closes: https://lore.kernel.org/r/CAMuHMdV9tX=TG7E_CrSF=2PY206tXf+_yYRuacG48EWEtJLo-Q@mail.gmail.com
> Signed-off-by: Petr Mladek <pmladek@...e.com>

Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>

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