linux-hardening - Re: [PATCH] xen/efi: refactor deprecated strncpy

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Date:   Tue, 19 Sep 2023 07:55:36 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Justin Stitt <justinstitt@...gle.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>
Cc:     xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org, Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH] xen/efi: refactor deprecated strncpy

On 11.09.23 20:59, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
> 
> `efi_loader_signature` has space for 4 bytes. We are copying "Xen" (3 bytes)
> plus a NUL-byte which makes 4 total bytes. With that being said, there is
> currently not a bug with the current `strncpy()` implementation in terms of
> buffer overreads but we should favor a more robust string interface
> either way.
> 
> A suitable replacement is `strscpy` [2] due to the fact that it guarantees
> NUL-termination on the destination buffer while being functionally the
> same in this case.
> 
> Link: 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>

Pushed to xen/tip.git for-linus-6.6a


Juergen


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