Re: [PATCH v2] atmel: replace deprecated strncpy with strscpy

[Kees Cook <keescook@chromium.org>]

On Thu, Oct 19, 2023 at 05:29:01PM +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 priv->firmware_id to be NUL-terminated based on its usage
> with seq_printf() and strlen() in atmel.c:
> 1420 |       seq_printf(m, "%s loaded by host\n", priv->firmware_id);
> ...
> 3884 |       if (strlen(priv->firmware_id) == 0) {
> 
> NUL-padding is not required, which is evident by the usage of a plain
> strcpy():
> 3891 |   strcpy(priv->firmware_id, "atmel_at76c502.bin");
> 
> 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 replace hard-coded lengths to be `sizeof(...)` for buffers
> that the compiler can detect the size for as this is less error prone.
> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strcpy [2]
> Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [3]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@vger.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@google.com>

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

-- 
Kees Cook