linux-hardening - Re: [PATCH RFC 2/3] powerpc/ps3: refactor strncpy usage attempt 2

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Message-ID: <202308141612.818819C6@keescook>
Date:   Mon, 14 Aug 2023 16:13:55 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Justin Stitt <justinstitt@...gle.com>
Cc:     Geoff Levand <geoff@...radead.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-hardening@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <nathan@...nel.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 2/3] powerpc/ps3: refactor strncpy usage attempt 2

On Fri, Aug 11, 2023 at 09:19:20PM +0000, Justin Stitt wrote:
> This approach tries to use `make_field` inside of `make_first_field`.
> This comes with some weird implementation as to get the same result we
> need to first subtract `index` from the `make_field` result whilst being
> careful with order of operations. We then have to add index back.

I think for readability, it's better to avoid the function composition.
The index subtraction undoes the earlier addition -- I say just leave it
separate.

i.e. I like option 1 of 3 the best.

-Kees

-- 
Kees Cook