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From: Guenter Roeck <linux@roeck-us.net>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rasmus Villemoes <rasmus.villemoes@prevas.dk>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	"Jason A. Donenfeld" <Jason@zx2c4.com>,
	linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org,
	linux-arch@vger.kernel.org, linux-toolchains@vger.kernel.org,
	Masahiro Yamada <masahiroy@kernel.org>,
	Kees Cook <keescook@chromium.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-m68k@lists.linux-m68k.org
Subject: Re: [PATCH v2] kbuild: treat char as always unsigned
Date: Wed, 21 Dec 2022 09:19:22 -0800	[thread overview]
Message-ID: <20221221171922.GA2470607@roeck-us.net> (raw)
In-Reply-To: <CAHk-=wj7FMFLr9AOW9Aa9ZMt1-Lu01_X8vLiaKosPyF2H-+ujA@mail.gmail.com>

On Wed, Dec 21, 2022 at 09:06:41AM -0800, Linus Torvalds wrote:
> On Wed, Dec 21, 2022 at 7:56 AM Guenter Roeck <linux@roeck-us.net> wrote:
> >
> > The above assumes an unsigned char as input to strcmp(). I consider that
> > a hypothetical problem because "comparing" strings with upper bits
> > set doesn't really make sense in practice (How does one compare Günter
> > against Gunter ? And how about Gǖnter ?). On the other side, the problem
> > observed here is real and immediate.
> 
> POSIX does actually specify "Günter" vs "Gunter".
> 
> The way strcmp is supposed to work is to return the sign of the
> difference between the byte values ("unsigned char").
> 
> But that sign has to be computed in 'int', not in 'signed char'.
> 
> So yes, the m68k implementation is broken regardless, but with a
> signed char it just happened to work for the US-ASCII case that the
> crypto case tested.
> 

I understand. I just prefer a known limited breakage to completely
broken code.

> I think the real fix is to just remove that broken implementation
> entirely, and rely on the generic one.

Perfectly fine with me.

Thanks,
Guenter

  reply	other threads:[~2022-12-21 17:21 UTC|newest]

Thread overview: 70+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-10-19 16:26 [PATCH] kbuild: treat char as always signed Jason A. Donenfeld
2022-10-19 16:54 ` Segher Boessenkool
2022-10-19 17:14   ` Linus Torvalds
2022-10-19 17:26     ` Linus Torvalds
2022-10-19 18:10       ` Nick Desaulniers
2022-10-19 18:35         ` Linus Torvalds
2022-10-19 19:23           ` Andy Shevchenko
2022-10-19 19:36             ` Linus Torvalds
2022-10-19 17:43     ` Segher Boessenkool
2022-10-19 18:11       ` Linus Torvalds
2022-10-19 18:20         ` Nick Desaulniers
2022-10-19 18:56           ` Linus Torvalds
2022-10-19 19:11             ` Kees Cook
2022-10-19 19:30               ` Linus Torvalds
2022-10-19 20:35                 ` Jason A. Donenfeld
2022-10-20  0:10                   ` Linus Torvalds
2022-10-20  3:11                     ` Jason A. Donenfeld
2022-10-19 20:15             ` Segher Boessenkool
2022-10-19 21:07         ` David Laight
2022-10-19 21:26           ` Segher Boessenkool
2022-10-20 10:41         ` Gabriel Paubert
2022-10-21 22:46           ` Linus Torvalds
2022-10-22  6:06             ` Gabriel Paubert
2022-10-22 18:16               ` Linus Torvalds
2022-10-23 20:23                 ` Gabriel Paubert
2022-10-25 23:00                   ` Kees Cook
2022-10-26  0:04                     ` Jason A. Donenfeld
2022-10-26 15:41                       ` Kees Cook
2022-10-19 19:54 ` Linus Torvalds
2022-10-19 20:23   ` Jason A. Donenfeld
2022-10-19 20:30     ` [PATCH v2] kbuild: treat char as always unsigned Jason A. Donenfeld
2022-10-19 23:56       ` Linus Torvalds
2022-10-20  0:02         ` Jason A. Donenfeld
2022-10-20  0:38           ` Linus Torvalds
2022-10-20  2:59             ` Jason A. Donenfeld
2022-10-20 18:41             ` Kees Cook
2022-10-21  1:01               ` Jason A. Donenfeld
2022-10-20 20:24         ` Segher Boessenkool
2022-10-24  9:24       ` Dan Carpenter
2022-10-24  9:30         ` Dan Carpenter
2022-10-24 16:33           ` Jason A. Donenfeld
2022-10-24 17:10             ` Linus Torvalds
2022-10-24 17:17               ` Jason A. Donenfeld
2022-10-25 19:22                 ` Kalle Valo
2022-10-25 10:16               ` David Laight
2022-10-24 15:17         ` Jason A. Donenfeld
2022-12-21 14:53       ` Guenter Roeck
2022-12-21 15:05         ` Geert Uytterhoeven
2022-12-21 15:23           ` Guenter Roeck
2022-12-21 15:29           ` Rasmus Villemoes
2022-12-21 15:56             ` Guenter Roeck
2022-12-21 17:06               ` Linus Torvalds
2022-12-21 17:19                 ` Guenter Roeck [this message]
2022-12-21 18:46                   ` Linus Torvalds
2022-12-21 19:08                     ` Linus Torvalds
2022-12-21 21:01                     ` Guenter Roeck
2022-12-22 13:05                     ` Geert Uytterhoeven
2022-12-22 10:41                 ` David Laight
     [not found]                   ` <f02e0ac7f2d805020a7ba66803aaff3e31b5eeff.camel@t-online.de>
2022-12-24  9:47                     ` Geert Uytterhoeven
2022-12-30 11:39                     ` David Laight
2022-12-30 13:13                       ` David Laight
2023-01-02  8:29                       ` Geert Uytterhoeven
2022-12-21 17:49               ` Andreas Schwab
2022-12-21 16:57             ` Geert Uytterhoeven
2022-10-19 20:58   ` [PATCH] kbuild: treat char as always signed David Laight
2022-10-26  0:10   ` make ctype ascii only? (was [PATCH] kbuild: treat char as always signed) Rasmus Villemoes
2022-10-26 18:10     ` Linus Torvalds
2022-10-27  7:59       ` Rasmus Villemoes
2022-10-27 18:28         ` Linus Torvalds
     [not found] ` <202210201618.8XhEGsLd-lkp@intel.com>
2022-10-20 16:33   ` [PATCH] kbuild: treat char as always signed Jason A. Donenfeld

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