linux-hardening - Re: [PATCH] cpufreq: refactor deprecated strncpy

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Message-ID: <202309142037.DAF02CD00@keescook>
Date:   Thu, 14 Sep 2023 20:37:13 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Justin Stitt <justinstitt@...gle.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH] cpufreq: refactor deprecated strncpy

On Wed, Sep 13, 2023 at 12:07:21AM +0000, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
> 
> We should prefer more robust and less ambiguous string interfaces.
> 
> Both `policy->last_governor` and `default_governor` are expected to be
> NUL-terminated which is shown by their heavy usage with other string
> apis like `strcmp`.
> 
> A suitable replacement is `strscpy` [2] due to the fact that it guarantees
> NUL-termination on the destination buffer.
> 
> 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>

All looks sensible to me.

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

-- 
Kees Cook