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

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Date: Tue, 10 Oct 2023 14:22:12 -0700
From: Jesse Brandeburg <jesse.brandeburg@...el.com>
To: Justin Stitt <justinstitt@...gle.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 10/10/2023 2:15 PM, 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).
> 


Please see my comments on the igbvf patch.