linux-kernel - Re: [PATCH] Add error check to hex2bin().

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Date:	Mon, 18 Jul 2011 22:49:22 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:	linux-security-module@...r.kernel.org,
	andriy.shevchenko@...ux.intel.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Add error check to hex2bin().

On Mon, Jul 18, 2011 at 14:48, Tetsuo Handa
<penguin-kernel@...ove.sakura.ne.jp> wrote:
> Currently, security/keys/ is the only user of hex2bin().
> Should I keep hex2bin() unmodified in case of bad input?
> If so, I'd like to make it as hex2bin_safe().
> ----------------------------------------
> [PATCH] Add error check to hex2bin().
>
> Since converting 2 hexadecimal letters into a byte with error checks is
> commonly used, we can replace multiple hex_to_bin() calls with single hex2bin()
> call by changing hex2bin() to do error checks.
>
> Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> ---
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index 953352a..186e9fc 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -374,7 +374,7 @@ static inline char *pack_hex_byte(char *buf, u8 byte)
>  }
>
>  extern int hex_to_bin(char ch);
> -extern void hex2bin(u8 *dst, const char *src, size_t count);
> +extern bool hex2bin(u8 *dst, const char *src, size_t count);
>
>  /*
>  * General tracing related utility functions - trace_printk(),
> diff --git a/lib/hexdump.c b/lib/hexdump.c
> index f5fe6ba..1524002 100644
> --- a/lib/hexdump.c
> +++ b/lib/hexdump.c
> @@ -38,14 +38,22 @@ EXPORT_SYMBOL(hex_to_bin);
>  * @dst: binary result
>  * @src: ascii hexadecimal string
>  * @count: result length
> + *
> + * Returns true on success, false in case of bad input.

What about making it return the number of unprocessed bytes left instead?
Then the caller knows where the problem lies. And zero would mean success.

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
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