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Subject: Re: [PATCH] sfc: replace deprecated strncpy with strscpy
To:     Justin Stitt <justinstitt@google.com>,
        Martin Habets <habetsm.xilinx@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>
Cc:     netdev@vger.kernel.org, linux-net-drivers@amd.com,
        linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
References: <20231012-strncpy-drivers-net-ethernet-sfc-mcdi-c-v1-1-478c8de1039d@google.com>
From:   Edward Cree <ecree.xilinx@gmail.com>
Message-ID: <c1b37796-76a2-b868-efd6-c09f41cee372@gmail.com>
Date:   Thu, 12 Oct 2023 21:55:40 +0100
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On 12/10/2023 21:38, 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@vger.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@google.com>

Acked-by: Edward Cree <ecree.xilinx@gmail.com>
but ideally we should just rip out the dead code instead.  If this
 patch gets taken as-is into net-next then I can probably do that
 in a follow-up.

-ed