netdev - Re: [PATCH] e100: replace deprecated strncpy with strscpy

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Message-ID: <20231010223526.2qc4q64txfoi64lq@google.com>
Date: Tue, 10 Oct 2023 22:35:26 +0000
From: Justin Stitt <justinstitt@...gle.com>
To: Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Tony Nguyen <anthony.l.nguyen@...el.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] e100: replace deprecated strncpy with strscpy

On Mon, Oct 09, 2023 at 11:41:01PM +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.
>
> The "...-1" pattern makes it evident that netdev->name is expected to be
> NUL-terminated.
>
> Meanwhile, it seems NUL-padding is not required due to alloc_etherdev
> zero-allocating the buffer.
>
> 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.
>
> This is in line with other uses of strscpy on netdev->name:
> $ rg "strscpy\(netdev\->name.*pci.*"
>
> drivers/net/ethernet/intel/e1000e/netdev.c
> 7455:   strscpy(netdev->name, pci_name(pdev), sizeof(netdev->name));
>
> drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> 10839:  strscpy(netdev->name, pci_name(pdev), sizeof(netdev->name));
>
> 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/intel/e100.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/intel/e100.c b/drivers/net/ethernet/intel/e100.c
> index d3fdc290937f..01f0f12035ca 100644
> --- a/drivers/net/ethernet/intel/e100.c
> +++ b/drivers/net/ethernet/intel/e100.c
> @@ -2841,7 +2841,7 @@ static int e100_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>  	netdev->netdev_ops = &e100_netdev_ops;
>  	netdev->ethtool_ops = &e100_ethtool_ops;
>  	netdev->watchdog_timeo = E100_WATCHDOG_PERIOD;
> -	strncpy(netdev->name, pci_name(pdev), sizeof(netdev->name) - 1);
> +	strscpy(netdev->name, pci_name(pdev), sizeof(netdev->name));
>
>  	nic = netdev_priv(netdev);
>  	netif_napi_add_weight(netdev, &nic->napi, e100_poll, E100_NAPI_WEIGHT);
>
> ---
> base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
> change-id: 20231009-strncpy-drivers-net-ethernet-intel-e100-c-4547179d9f2c
>
> Best regards,
> --
> Justin Stitt <justinstitt@...gle.com>
>

Hi, this patch was bundled up with some others. It has a new home:

https://lore.kernel.org/all/20231010-netdev-replace-strncpy-resend-as-series-v1-0-caf9f0f2f021@google.com/