linux-hardening - Re: [PATCH] wifi: wlcore: replace deprecated strncpy with strscpy

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Date: Wed, 18 Oct 2023 22:30:53 -0700
From: Kees Cook <keescook@...omium.org>
To: Justin Stitt <justinstitt@...gle.com>
Cc: Kalle Valo <kvalo@...nel.org>, linux-wireless@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] wifi: wlcore: replace deprecated strncpy with strscpy

On Wed, Oct 18, 2023 at 09:36:56PM +0000, Justin Stitt wrote:
> strncpy() is deprecated for use on NUL-terminated destination strings
> [1] and as such we should prefer more robust and less ambiguous string
> interfaces.
> 
> We expect wl->chip.fw_ver_str to be NUL-terminated based on its usage
> with DRIVER_STATE_PRINT_STR() in debugfs.c:
> 491 | DRIVER_STATE_PRINT_STR(chip.fw_ver_str);
> ... which uses DRIVER_STATE_PRINT():
> 444 | #define DRIVER_STATE_PRINT_STR(x)  DRIVER_STATE_PRINT(x, "%s")
> ... which relies on scnprintf:
> 434 | #define DRIVER_STATE_PRINT(x, fmt)   \
> 435 | 	(res += scnprintf(buf + res, DRIVER_STATE_BUF_LEN - res,\
> 436 | 			  #x " = " fmt "\n", wl->x))
> 
> Moreover, NUL-padding is not required.
> 
> Considering the above, a suitable replacement is `strscpy` [2] due to
> the fact that it guarantees NUL-termination on the destination buffer
> without unnecessarily NUL-padding.
> 
> Link: https://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
> Similar-to: https://lore.kernel.org/all/20231018-strncpy-drivers-net-wireless-ti-wl18xx-main-c-v2-1-ab828a491ce5@google.com/
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>

Yup, looks good.

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook