linux-hardening - Re: [PATCH] i2c: replace deprecated strncpy

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Date:   Wed, 20 Sep 2023 07:33:11 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Justin Stitt <justinstitt@...gle.com>
Cc:     Andi Shyti <andi.shyti@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-i2c@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] i2c: replace deprecated strncpy

On Wed, Sep 20, 2023 at 11:07:35AM +0000, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
> 
> We should prefer more robust and less ambiguous string interfaces.
> 
> `info.type` is expected to be NUL-terminated judging by its use in
> `i2c_new_client_device()` wherein it is used to populate `client->name`:
> |	strscpy(client->name, info->type, sizeof(client->name));
> 
> NUL-padding is not required and even if it was, `client` is already
> zero-initialized.
> 
> Considering the two points from 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
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>

Looks like a straight replacement. Thanks!

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

-- 
Kees Cook