linux-hardening - Re: [PATCH] net: liquidio: replace deprecated strncpy with strscpy

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Message-ID: <202310051615.4DD6C6C6D@keescook>
Date: Thu, 5 Oct 2023 16:16:07 -0700
From: Kees Cook <keescook@...omium.org>
To: Justin Stitt <justinstitt@...gle.com>
Cc: Derek Chickles <dchickles@...vell.com>,
	Satanand Burla <sburla@...vell.com>,
	Felix Manlunas <fmanlunas@...vell.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-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH] net: liquidio: replace deprecated strncpy with
 strscpy_pad

On Thu, Oct 05, 2023 at 09:41:01PM +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 know `fw_type` must be NUL-terminated based on use here:
> |       static bool fw_type_is_auto(void)
> |       {
> |       	return strncmp(fw_type, LIO_FW_NAME_TYPE_AUTO,
> |       		       sizeof(LIO_FW_NAME_TYPE_AUTO)) == 0;
> |       }
> ...and here
> |       module_param_string(fw_type, fw_type, sizeof(fw_type), 0444);
> 
> Let's opt to NUL-pad the destination buffer as well so that we maintain
> the same exact behavior that `strncpy` provided here.
> 
> A suitable replacement is `strscpy_pad` due to the fact that it
> guarantees both NUL-termination and NUL-padding on the destination
> buffer.
> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> 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 safe replacement with strscpy_pad().

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

> ---
> Note: build-tested only.
> ---
>  drivers/net/ethernet/cavium/liquidio/lio_main.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/cavium/liquidio/lio_main.c b/drivers/net/ethernet/cavium/liquidio/lio_main.c
> index 100daadbea2a..34f02a8ec2ca 100644
> --- a/drivers/net/ethernet/cavium/liquidio/lio_main.c
> +++ b/drivers/net/ethernet/cavium/liquidio/lio_main.c
> @@ -1689,7 +1689,7 @@ static int load_firmware(struct octeon_device *oct)
>  
>  	if (fw_type_is_auto()) {
>  		tmp_fw_type = LIO_FW_NAME_TYPE_NIC;
> -		strncpy(fw_type, tmp_fw_type, sizeof(fw_type));
> +		strscpy_pad(fw_type, tmp_fw_type, sizeof(fw_type));
>  	} else {
>  		tmp_fw_type = fw_type;
>  	}
> 
> ---
> base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
> change-id: 20231005-strncpy-drivers-net-ethernet-cavium-liquidio-lio_main-c-b05f78661635
> 
> Best regards,
> --
> Justin Stitt <justinstitt@...gle.com>
> 
> 

-- 
Kees Cook