linux-kernel - Re: [PATCH] accessibility: speakup: refactor deprecated strncpy

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Message-ID: <20230824215806.3ulejc2gsapcl2mw@begin>
Date:   Thu, 24 Aug 2023 23:58:06 +0200
From:   Samuel Thibault <samuel.thibault@...-lyon.org>
To:     Justin Stitt <justinstitt@...gle.com>
Cc:     William Hubbs <w.d.hubbs@...il.com>,
        Chris Brannon <chris@...-brannons.com>,
        Kirk Reiser <kirk@...sers.ca>, speakup@...ux-speakup.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] accessibility: speakup: refactor deprecated strncpy

Justin Stitt, le jeu. 24 août 2023 21:44:29 +0000, a ecrit:
> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
> 
> Use `strscpy` as it guarantees NUL-termination of its destination buffer [2]
> which allows for simpler and less ambiguous code.
> 
> Also, change `strlen(buf)` to `strlen(ptr)` to be consistent with
> further usage within the scope of the function. Note that these are
> equivalent:
> |419 	const char *ptr = buf;
> 
> Link: www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings[1]
> Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@...r.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>

Reviewed-by: Samuel Thibault <samuel.thibault@...-lyon.org>

> ---
> Note: build-tested only.
> ---
>  drivers/accessibility/speakup/kobjects.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/accessibility/speakup/kobjects.c b/drivers/accessibility/speakup/kobjects.c
> index a7522d409802..8aa416c5f3fc 100644
> --- a/drivers/accessibility/speakup/kobjects.c
> +++ b/drivers/accessibility/speakup/kobjects.c
> @@ -422,12 +422,11 @@ static ssize_t synth_direct_store(struct kobject *kobj,
>  	if (!synth)
>  		return -EPERM;
>  
> -	len = strlen(buf);
> +	len = strlen(ptr);
>  	spin_lock_irqsave(&speakup_info.spinlock, flags);
>  	while (len > 0) {
>  		bytes = min_t(size_t, len, 250);
> -		strncpy(tmp, ptr, bytes);
> -		tmp[bytes] = '\0';
> +		strscpy(tmp, ptr, bytes);
>  		string_unescape_any_inplace(tmp);
>  		synth_printf("%s", tmp);
>  		ptr += bytes;
> 
> ---
> base-commit: f9604036a3fb6149badf346994b46b03f9292db7
> change-id: 20230824-strncpy-drivers-accessibility-speakup-kobjects-c-4009e7df0936
> 
> Best regards,
> --
> Justin Stitt <justinstitt@...gle.com>
>