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

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Message-ID: <202310191606.93920741B@keescook>
Date: Thu, 19 Oct 2023 16:06:44 -0700
From: Kees Cook <keescook@...omium.org>
To: Justin Stitt <justinstitt@...gle.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH] ACPI: replace deprecated strncpy with strscpy

On Thu, Oct 19, 2023 at 10:47:58PM +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 know dev->name should be NUL-terminated based on the presence of a
> manual NUL-byte assignment.
> 
> NUL-padding is not required as dev is already zero-allocated which
> renders any further NUL-byte assignments redundant:
> dev = pnp_alloc_dev(&pnpacpi_protocol, num, pnpid); --->
>   dev = kzalloc(sizeof(struct pnp_dev), GFP_KERNEL);
> 
> 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. This simplifies the code and makes
> the intent/behavior more obvious.
> 
> 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>

Looks clean to me!

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook