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Date:   Thu, 5 Oct 2023 16:14:31 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Justin Stitt <justinstitt@google.com>
Cc:     Derek Chickles <dchickles@marvell.com>,
        Satanand Burla <sburla@marvell.com>,
        Felix Manlunas <fmanlunas@marvell.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] liquidio: replace deprecated strncpy/strcpy with strscpy
Message-ID: <202310051610.01453F60F@keescook>
References: <20231005-strncpy-drivers-net-ethernet-cavium-liquidio-lio_ethtool-c-v1-1-ab565ab4d197@google.com>
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In-Reply-To: <20231005-strncpy-drivers-net-ethernet-cavium-liquidio-lio_ethtool-c-v1-1-ab565ab4d197@google.com>
Precedence: bulk

On Thu, Oct 05, 2023 at 09:33:19PM +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.
> 
> NUL-padding is not required as drvinfo is memset to 0:
> |	memset(drvinfo, 0, sizeof(struct ethtool_drvinfo));
> 
> 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>
> ---
> Note: build-tested only.
> ---
>  drivers/net/ethernet/cavium/liquidio/lio_ethtool.c | 18 ++++++++++--------
>  1 file changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/ethernet/cavium/liquidio/lio_ethtool.c b/drivers/net/ethernet/cavium/liquidio/lio_ethtool.c
> index 9d56181a301f..d3e07b6ed5e1 100644
> --- a/drivers/net/ethernet/cavium/liquidio/lio_ethtool.c
> +++ b/drivers/net/ethernet/cavium/liquidio/lio_ethtool.c
> @@ -442,10 +442,11 @@ lio_get_drvinfo(struct net_device *netdev, struct ethtool_drvinfo *drvinfo)
>  	oct = lio->oct_dev;
>  
>  	memset(drvinfo, 0, sizeof(struct ethtool_drvinfo));

struct ethtool_drvinfo {
        char    driver[32];
	...
        char    fw_version[ETHTOOL_FWVERS_LEN];
        char    bus_info[ETHTOOL_BUSINFO_LEN];

> -	strcpy(drvinfo->driver, "liquidio");
> +	strscpy(drvinfo->driver, "liquidio", sizeof(drvinfo->driver));

Yup, this is basically what FORTIFY_SOURCE will do automatically to
strcpy().

> -	strncpy(drvinfo->fw_version, oct->fw_info.liquidio_firmware_version,
> -		ETHTOOL_FWVERS_LEN);
> +	strscpy(drvinfo->fw_version, oct->fw_info.liquidio_firmware_version,
> +		sizeof(drvinfo->fw_version));

Yup, ETHTOOL_FWVERS_LEN == sizeof(drvinfo->fw_version)

> -	strncpy(drvinfo->bus_info, pci_name(oct->pci_dev), 32);
> +	strscpy(drvinfo->bus_info, pci_name(oct->pci_dev),
> +		sizeof(drvinfo->bus_info));

Yup, ETHTOOL_BUSINFO_LEN == sizeof(drvinfo->bus_info)

>  }
>  
>  static void
> @@ -458,10 +459,11 @@ lio_get_vf_drvinfo(struct net_device *netdev, struct ethtool_drvinfo *drvinfo)
>  	oct = lio->oct_dev;
>  
>  	memset(drvinfo, 0, sizeof(struct ethtool_drvinfo));
> -	strcpy(drvinfo->driver, "liquidio_vf");
> -	strncpy(drvinfo->fw_version, oct->fw_info.liquidio_firmware_version,
> -		ETHTOOL_FWVERS_LEN);
> -	strncpy(drvinfo->bus_info, pci_name(oct->pci_dev), 32);
> +	strscpy(drvinfo->driver, "liquidio_vf", sizeof(drvinfo->driver));
> +	strscpy(drvinfo->fw_version, oct->fw_info.liquidio_firmware_version,
> +		sizeof(drvinfo->fw_version));
> +	strscpy(drvinfo->bus_info, pci_name(oct->pci_dev),
> +		sizeof(drvinfo->bus_info));
>  }

Yup, looks good.

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

>  
>  static int
> 
> ---
> base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
> change-id: 20231005-strncpy-drivers-net-ethernet-cavium-liquidio-lio_ethtool-c-b6932c0f80f1
> 
> Best regards,
> --
> Justin Stitt <justinstitt@google.com>
> 
> 

-- 
Kees Cook