linux-kernel - Re: [PATCH] netfilter: nf_tables: replace deprecated strncpy with strscpy

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Message-ID: <20240913111732.GV572255@kernel.org>
Date: Fri, 13 Sep 2024 12:17:32 +0100
From: Simon Horman <horms@...nel.org>
To: Justin Stitt <justinstitt@...gle.com>
Cc: Pablo Neira Ayuso <pablo@...filter.org>,
	Jozsef Kadlecsik <kadlec@...filter.org>,
	Roopa Prabhu <roopa@...dia.com>,
	Nikolay Aleksandrov <razor@...ckwall.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netfilter-devel@...r.kernel.org, coreteam@...filter.org,
	bridge@...ts.linux.dev, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
	Kees Cook <kees@...nel.org>
Subject: Re: [PATCH] netfilter: nf_tables: replace deprecated strncpy with
 strscpy_pad

On Mon, Sep 09, 2024 at 03:48:39PM -0700, 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.
> 
> In this particular instance, the usage of strncpy() is fine and works as
> expected. However, towards the goal of [2], we should consider replacing
> it with an alternative as many instances of strncpy() are bug-prone. Its
> removal from the kernel promotes better long term health for the
> codebase.
> 
> The current usage of strncpy() likely just wants the NUL-padding
> behavior offered by strncpy() and doesn't care about the
> NUL-termination. Since the compiler doesn't know the size of @dest, we
> can't use strtomem_pad(). Instead, use strscpy_pad() which behaves
> functionally the same as strncpy() in this context -- as we expect
> br_dev->name to be NUL-terminated itself.
> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://github.com/KSPP/linux/issues/90 [2]
> Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html
> Cc: Kees Cook <keescook@...omium.org>
> Cc: linux-hardening@...r.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>
> ---
> Note: build-tested only.

Reviewed-by: Simon Horman <horms@...nel.org>