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

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Message-ID: <20231010224245.i57oix72csm7kjp7@google.com>
Date: Tue, 10 Oct 2023 22:42:45 +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] igc: replace deprecated strncpy with strscpy

On Tue, Oct 10, 2023 at 09:15:39PM +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 netdev->name to be NUL-terminated based on its use with format
> strings:
> |       if (q_vector->rx.ring && q_vector->tx.ring)
> |               sprintf(q_vector->name, "%s-TxRx-%u", netdev->name,
>
> Furthermore, we do not need NUL-padding as netdev is already
> zero-allocated:
> |       netdev = alloc_etherdev_mq(sizeof(struct igc_adapter),
> |                                  IGC_MAX_TX_QUEUES);
> ...
> alloc_etherdev() -> alloc_etherdev_mq() -> alloc_etherdev_mqs() ->
> alloc_netdev_mqs() ...
> |       p = kvzalloc(alloc_size, GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL);
>
> 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.
>
> Let's also opt for the more idiomatic strscpy usage of (dest, src,
> sizeof(dest)) instead of (dest, src, SOME_LEN).
>
> 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/igc/igc_main.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
> index 98de34d0ce07..e9bb403bbacf 100644
> --- a/drivers/net/ethernet/intel/igc/igc_main.c
> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> @@ -6935,7 +6935,7 @@ static int igc_probe(struct pci_dev *pdev,
>  	 */
>  	igc_get_hw_control(adapter);
>
> -	strncpy(netdev->name, "eth%d", IFNAMSIZ);
> +	strscpy(netdev->name, "eth%d", sizeof(netdev->name));
>  	err = register_netdev(netdev);
>  	if (err)
>  		goto err_register;
>
> ---
> base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
> change-id: 20231010-strncpy-drivers-net-ethernet-intel-igc-igc_main-c-26efa209ddb5
>
> 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/