linux-kernel - Re: [PATCH] riscv: use strscpy to replace strlcpy

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Message-ID: <mhng-ec52f7a2-7fe9-4109-b326-a92af8b8205b@palmerdabbelt-glaptop>
Date:   Wed, 25 Aug 2021 23:08:01 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     wangborong@...rlc.com
CC:     Paul Walmsley <paul.walmsley@...ive.com>, aou@...s.berkeley.edu,
        Atish Patra <Atish.Patra@....com>,
        Anup Patel <Anup.Patel@....com>, wangkefeng.wang@...wei.com,
        mick@....forth.gr, alex@...ti.fr, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org, wangborong@...rlc.com
Subject:     Re: [PATCH] riscv: use strscpy to replace strlcpy

On Sat, 07 Aug 2021 00:14:27 PDT (-0700), wangborong@...rlc.com wrote:
> The strlcpy should not be used because it doesn't limit the source
> length. As linus says, it's a completely useless function if you
> can't implicitly trust the source string - but that is almost always
> why people think they should use it! All in all the BSD function
> will lead some potential bugs.
>
> But the strscpy doesn't require reading memory from the src string
> beyond the specified "count" bytes, and since the return value is
> easier to error-check than strlcpy()'s. In addition, the implementation
> is robust to the string changing out from underneath it, unlike the
> current strlcpy() implementation.
>
> Thus, We prefer using strscpy instead of strlcpy.
>
> Signed-off-by: Jason Wang <wangborong@...rlc.com>
> ---
>  arch/riscv/kernel/setup.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
> index 18bd0e4bc36c..2dc62ebc0001 100644
> --- a/arch/riscv/kernel/setup.c
> +++ b/arch/riscv/kernel/setup.c
> @@ -255,7 +255,7 @@ static void __init parse_dtb(void)
>
>  	pr_err("No DTB passed to the kernel\n");
>  #ifdef CONFIG_CMDLINE_FORCE
> -	strlcpy(boot_command_line, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
> +	strscpy(boot_command_line, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
>  	pr_info("Forcing kernel command line to: %s\n", boot_command_line);
>  #endif
>  }

Thanks, this is on for-next.