Re: [PATCH v2] drivers: misc: ti-st: replace deprecated strncpy with strscpy

From: Kees Cook <keescook@chromium.org>
To: Justin Stitt <justinstitt@google.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH v2] drivers: misc: ti-st: replace deprecated strncpy with strscpy
Date: Tue, 3 Oct 2023 16:46:45 -0700	[thread overview]
Message-ID: <202310031646.C94326A6@keescook> (raw)
In-Reply-To: <20231003-strncpy-drivers-misc-ti-st-st_kim-c-v2-1-79630447b0a1@google.com>

On Tue, Oct 03, 2023 at 10:23:07PM +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 both `kim_data->dev_name` and `kim_gdata->dev_name` to be
> NUL-terminated.
> 
> `kim_data->dev_name` seems to not require NUL-padding.
> 
> `kim_gdata` is already zero-allocated and as such does not require
> NUL-padding:
> |       kim_gdata = kzalloc(sizeof(struct kim_data_s), GFP_KERNEL);
> 
> 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.
> 
> Let's also opt to use the more idiomatic strscpy usage of:
> strscpy(dest, src, sizeof(dest))
> 
> 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@vger.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@google.com>

Thanks for the adjustment. This looks right to me now.

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

-- 
Kees Cook