linux-kernel - Re: [PATCH v2] HID: uhid: replace deprecated strncpy with strscpy

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Message-ID: <202310031641.53DE6178@keescook>
Date:   Tue, 3 Oct 2023 16:41:50 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Justin Stitt <justinstitt@...gle.com>
Cc:     David Rheinsberg <david@...dahead.eu>,
        Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2] HID: uhid: replace deprecated strncpy with strscpy

On Tue, Oct 03, 2023 at 09:01:58PM +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.
> 
> A suitable replacement is `strscpy` [2] due to the fact that it
> guarantees NUL-termination on the destination buffer without
> unnecessarily NUL-padding.
> 
> Furthermore, let's make sure `hid->xyz` and `ev->u.create2.xyz` are the
> same size at compile time to prevent silent truncation.
> 
> With these changes, it is abundantly clear what the intent and behavior
> of the code is -- We are getting a string to string copy with
> NUL-termination and no truncation.
> 
> 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
> Cc: Kees Cook <keescook@...omium.org>
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>

Great! This looks much simpler to me. Thanks for adjusting it.

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

-- 
Kees Cook