linux-kernel - Re: [PATCH] m68k: mm: Replace deprecated strncpy() with strscpy()

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Message-ID: <202502191820.DA875C6@keescook>
Date: Wed, 19 Feb 2025 18:21:54 -0800
From: Kees Cook <kees@...nel.org>
To: Thorsten Blum <thorsten.blum@...ux.dev>
Cc: Geert Uytterhoeven <geert@...ux-m68k.org>,
	Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>,
	linux-hardening@...r.kernel.org, linux-m68k@...ts.linux-m68k.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] m68k: mm: Replace deprecated strncpy() with strscpy()

On Thu, Feb 13, 2025 at 03:10:36PM +0100, Thorsten Blum wrote:
> strncpy() is deprecated for NUL-terminated destination buffers. Use
> strscpy() instead and remove the manual NUL-termination.
> 
> Compile-tested only.
> 
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@...r.kernel.org
> Signed-off-by: Thorsten Blum <thorsten.blum@...ux.dev>
> ---
>  arch/m68k/kernel/setup_mm.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/arch/m68k/kernel/setup_mm.c b/arch/m68k/kernel/setup_mm.c
> index 15c1a595a1de..48ce67947678 100644
> --- a/arch/m68k/kernel/setup_mm.c
> +++ b/arch/m68k/kernel/setup_mm.c
> @@ -243,8 +243,7 @@ void __init setup_arch(char **cmdline_p)
>  	setup_initial_init_mm((void *)PAGE_OFFSET, _etext, _edata, _end);
>  
>  #if defined(CONFIG_BOOTPARAM)
> -	strncpy(m68k_command_line, CONFIG_BOOTPARAM_STRING, CL_SIZE);
> -	m68k_command_line[CL_SIZE - 1] = 0;
> +	strscpy(m68k_command_line, CONFIG_BOOTPARAM_STRING, CL_SIZE);
>  #endif /* CONFIG_BOOTPARAM */
>  	process_uboot_commandline(&m68k_command_line[0], CL_SIZE);
>  	*cmdline_p = m68k_command_line;

m68k_command_line lives in rwdata, so it should be 0-initialized by
default, so there should be no behavioral difference here (i.e. it will
be zero-padded), and it is used as a C String, so there was unlikely to
be anything depending on the NUL-padding.

Reviewed-by: Kees Cook <kees@...nel.org>

-- 
Kees Cook