linux-hardening - Re: [PATCH] i40e: use scnprintf over strncpy+strncat

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Date: Tue, 10 Oct 2023 14:21:34 -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] i40e: use scnprintf over strncpy+strncat

On 10/10/2023 1:53 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.
> 
> Moreover, `strncat` shouldn't really be used either as per
> fortify-string.h:
>  * Do not use this function. While FORTIFY_SOURCE tries to avoid
>  * read and write overflows, this is only possible when the sizes
>  * of @p and @q are known to the compiler. Prefer building the
>  * string with formatting, via scnprintf() or similar.
> 
> Instead, use `scnprintf` with "%s%s" format string. This code is now
> more readable and robust.


Please see my comments on the igbvf patch.