linux-hardening - Re: [PATCH] m68k: cmpxchg: Dereference matching size

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Message-ID: <CAMuHMdVRrD+2zKoHxAaQdDuiK5JFDanbv0SJ91OdWfx+eyekPQ@mail.gmail.com>
Date:   Thu, 3 Feb 2022 09:13:30 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Greg Ungerer <gerg@...ux-m68k.org>,
        Mark Rutland <mark.rutland@....com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Arnd Bergmann <arnd@...db.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH] m68k: cmpxchg: Dereference matching size

Hi Kees,

On Wed, Feb 2, 2022 at 11:53 PM Kees Cook <keescook@...omium.org> wrote:
> Similar to the recent arm64 fix[1], avoid overly wide casts in the cmpxchg
> implementation. Avoid this warning under -Warray-bounds with GCC 11:
>
> net/sched/cls_tcindex.c: In function 'tcindex_set_parms':
> ./arch/m68k/include/asm/cmpxchg.h:64:17: warning: array subscript 'volatile struct __xchg_dummy[0]' is partly outside array bounds of 'struct tcf_result[1]' [-Warray-bounds]
>    64 |                 __asm__ __volatile__
>       |                 ^~~~~~~
> net/sched/cls_tcindex.c:338:27: note: while referencing 'cr'
>   338 |         struct tcf_result cr = {};
>       |                           ^~
>
> No binary output differences are seen from this change.
>
> [1] commit 3364c6ce23c6 ("arm64: atomics: lse: Dereference matching size")
>
> Signed-off-by: Kees Cook <keescook@...omium.org>

Thanks for your patch!

Reviewed-by: Geert Uytterhoeven <geert@...ux-m68k.org>

Do you want me to queue this in the m68k for-v5.18 branch, or do
you want to take it yourself, together with commit a8712a32665f9b1a
("Makefile: Enable -Warray-bounds") in linux-next that triggers this?
In case of the latter:
Acked-by: Geert Uytterhoeven <geert@...ux-m68k.org>

Please let me know. Thanks!

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds