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Date:   Tue, 10 Oct 2023 22:38:46 +0000
From:   Justin Stitt <justinstitt@google.com>
To:     Jesse Brandeburg <jesse.brandeburg@intel.com>,
        Tony Nguyen <anthony.l.nguyen@intel.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>
Cc:     intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH] igb: replace deprecated strncpy with strscpy
Message-ID: <20231010223846.fxmqzdjelxfmio7u@google.com>
References: <20231010-strncpy-drivers-net-ethernet-intel-igb-igb_main-c-v1-1-d796234a8abf@google.com>
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In-Reply-To: <20231010-strncpy-drivers-net-ethernet-intel-igb-igb_main-c-v1-1-d796234a8abf@google.com>
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On Tue, Oct 10, 2023 at 09:07:59PM +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 see that netdev->name is expected to be NUL-terminated based on its
> usage with format strings:
> |       sprintf(q_vector->name, "%s-TxRx-%u", netdev->name,
> |               q_vector->rx.ring->queue_index);
>
> Furthermore, NUL-padding is not required as netdev is already
> zero-allocated:
> |       netdev = alloc_etherdev_mq(sizeof(struct igb_adapter),
> |                                  IGB_MAX_TX_QUEUES);
> ...
> 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.
>
> 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/intel/igb/igb_main.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
> index 76b34cee1da3..9de103bd3ad3 100644
> --- a/drivers/net/ethernet/intel/igb/igb_main.c
> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> @@ -3264,7 +3264,7 @@ static int igb_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>  	igb_set_ethtool_ops(netdev);
>  	netdev->watchdog_timeo = 5 * HZ;
>
> -	strncpy(netdev->name, pci_name(pdev), sizeof(netdev->name) - 1);
> +	strscpy(netdev->name, pci_name(pdev), sizeof(netdev->name));
>
>  	netdev->mem_start = pci_resource_start(pdev, 0);
>  	netdev->mem_end = pci_resource_end(pdev, 0);
>
> ---
> base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
> change-id: 20231010-strncpy-drivers-net-ethernet-intel-igb-igb_main-c-b259e3f289d3
>
> Best regards,
> --
> Justin Stitt <justinstitt@google.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/