linux-kernel - Re: [PATCH] sfc: replace deprecated strncpy with strscpy

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Message-ID: <202310121402.7A27AB9@keescook>
Date:   Thu, 12 Oct 2023 14:19:13 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Justin Stitt <justinstitt@...gle.com>
Cc:     Edward Cree <ecree.xilinx@...il.com>,
        Martin Habets <habetsm.xilinx@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        linux-net-drivers@....com, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH] sfc: replace deprecated strncpy with strscpy

On Thu, Oct 12, 2023 at 08:38:19PM +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.
> 
> `desc` is expected to be NUL-terminated as evident by the manual
> NUL-byte assignment. Moreover, NUL-padding does not seem to be
> necessary.
> 
> The only caller of efx_mcdi_nvram_metadata() is
> efx_devlink_info_nvram_partition() which provides a NULL for `desc`:
> |       rc = efx_mcdi_nvram_metadata(efx, partition_type, NULL, version, NULL, 0);
> 
> Due to this, I am not sure this code is even reached but we should still
> favor something other than strncpy.
> 
> 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
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>

Looks correct to me!

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

-- 
Kees Cook