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Date:   Mon, 11 Dec 2023 23:22:55 +0000
From:   "Russell King (Oracle)" <linux@armlinux.org.uk>
To:     Justin Stitt <justinstitt@google.com>
Cc:     Andrew Lunn <andrew@lunn.ch>,
        Heiner Kallweit <hkallweit1@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH v3] net: mdio-gpio: replace deprecated strncpy with
 strscpy
Message-ID: <ZXeZz4JcJAIMJLTy@shell.armlinux.org.uk>
References: <20231211-strncpy-drivers-net-mdio-mdio-gpio-c-v3-1-76dea53a1a52@google.com>
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In-Reply-To: <20231211-strncpy-drivers-net-mdio-mdio-gpio-c-v3-1-76dea53a1a52@google.com>
Sender: Russell King (Oracle) <linux@armlinux.org.uk>
Precedence: bulk

On Mon, Dec 11, 2023 at 07:10:00PM +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 new_bus->id to be NUL-terminated but not NUL-padded based on
> its prior assignment through snprintf:
> |       snprintf(new_bus->id, MII_BUS_ID_SIZE, "gpio-%x", bus_id);
> 
> Due to this, a suitable replacement is `strscpy` [2] due to the fact
> that it guarantees NUL-termination on the destination buffer without
> unnecessarily NUL-padding.
> 
> We can also use sizeof() instead of a length macro as this more closely
> ties the maximum buffer size to the destination buffer. Do this for two
> instances.
> 
> 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>

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

Thanks!

-- 
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