linux-hardening - Re: [PATCH] net: ax88796c: replace deprecated strncpy with strscpy

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Date: Thu, 05 Oct 2023 10:40:46 +0200
From: Lukasz Stelmach <l.stelmach@...sung.com>
To: Justin Stitt <justinstitt@...gle.com>
Cc: "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: ax88796c: replace deprecated strncpy with strscpy

It was <2023-10-05 czw 01:06>, when 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.
>
> A suitable replacement is `strscpy` [2] due to the fact that it
> guarantees NUL-termination on the destination buffer without
> unnecessarily NUL-padding.
>
> It should be noted that there doesn't currently exist a bug here as
> DRV_NAME is a small string literal which means no overread bugs are
> present.
>
> Also to note, other ethernet drivers are using strscpy in a similar
> pattern:
> |       dec/tulip/tulip_core.c
> |       861:    strscpy(info->driver, DRV_NAME, sizeof(info->driver));
> |
> |       8390/ax88796.c
> |       582:    strscpy(info->driver, DRV_NAME, sizeof(info->driver));
> |
> |       dec/tulip/dmfe.c
> |       1077:   strscpy(info->driver, DRV_NAME, sizeof(info->driver));
> |
> |       8390/etherh.c
> |       558:    strscpy(info->driver, DRV_NAME, sizeof(info->driver));
>
> 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>
> ---
> Note: build-tested only.
> ---
>  drivers/net/ethernet/asix/ax88796c_ioctl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>

Reviewed-by: Lukasz Stelmach <l.stelmach@...sung.com>

> diff --git a/drivers/net/ethernet/asix/ax88796c_ioctl.c b/drivers/net/ethernet/asix/ax88796c_ioctl.c
> index 916ae380a004..7d2fe2e5af92 100644
> --- a/drivers/net/ethernet/asix/ax88796c_ioctl.c
> +++ b/drivers/net/ethernet/asix/ax88796c_ioctl.c
> @@ -24,7 +24,7 @@ static void
>  ax88796c_get_drvinfo(struct net_device *ndev, struct ethtool_drvinfo *info)
>  {
>  	/* Inherit standard device info */
> -	strncpy(info->driver, DRV_NAME, sizeof(info->driver));
> +	strscpy(info->driver, DRV_NAME, sizeof(info->driver));
>  }
>  
>  static u32 ax88796c_get_msglevel(struct net_device *ndev)
>
> ---
> base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
> change-id: 20231005-strncpy-drivers-net-ethernet-asix-ax88796c_ioctl-c-56af20b7d992
>
> Best regards,
> --
> Justin Stitt <justinstitt@...gle.com>
>
>
>

-- 
Łukasz Stelmach
Samsung R&D Institute Poland
Samsung Electronics

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