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From:   "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Fri, 20 Oct 2023 19:49:22 +0200
Message-ID: <CAJZ5v0j5bk+RM3Tvixp5oX48EE_7hDoO5sd-Vrmwu=iz5kO7jQ@mail.gmail.com>
Subject: Re: [PATCH] ACPI: replace deprecated strncpy with strscpy
To:     Kees Cook <keescook@chromium.org>,
        Justin Stitt <justinstitt@google.com>
Cc:     "Rafael J. Wysocki" <rafael@kernel.org>,
        Len Brown <lenb@kernel.org>, linux-acpi@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
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On Fri, Oct 20, 2023 at 1:06 AM Kees Cook <keescook@chromium.org> wrote:
>
> 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@vger.kernel.org
> > Signed-off-by: Justin Stitt <justinstitt@google.com>
>
> Looks clean to me!
>
> Reviewed-by: Kees Cook <keescook@chromium.org>

Applied as 6.7 material, thanks!