Date:   Mon, 22 Nov 2021 12:47:28 -0800
From:   Kees Cook <keescook@chromium.org>
To:     Michael Ellerman <mpe@ellerman.id.au>
Cc:     LEROY Christophe <christophe.leroy@csgroup.eu>,
        kernel test robot <lkp@intel.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Sudeep Holla <sudeep.holla@arm.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Nicholas Piggin <npiggin@gmail.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
        "linux-hardening@vger.kernel.org" <linux-hardening@vger.kernel.org>
Subject: Re: [PATCH] powerpc/signal32: Use struct_group() to zero spe regs
Message-ID: <202111221247.B385EA2A8@keescook>
References: <20211118203604.1288379-1-keescook@chromium.org>
 <1e312cbd-cd52-ddce-f839-db765173c526@csgroup.eu>
 <87ilwkrbhz.fsf@mpe.ellerman.id.au>
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On Mon, Nov 22, 2021 at 04:43:36PM +1100, Michael Ellerman wrote:
> LEROY Christophe <christophe.leroy@csgroup.eu> writes:
> > Le 18/11/2021 ? 21:36, Kees Cook a ?crit?:
> >> In preparation for FORTIFY_SOURCE performing compile-time and run-time
> >> field bounds checking for memset(), avoid intentionally writing across
> >> neighboring fields.
> >> 
> >> Add a struct_group() for the spe registers so that memset() can correctly reason
> >> about the size:
> >> 
> >>     In function 'fortify_memset_chk',
> >>         inlined from 'restore_user_regs.part.0' at arch/powerpc/kernel/signal_32.c:539:3:
> >>     >> include/linux/fortify-string.h:195:4: error: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning]
> >>       195 |    __write_overflow_field();
> >>           |    ^~~~~~~~~~~~~~~~~~~~~~~~
> >> 
> >> Reported-by: kernel test robot <lkp@intel.com>
> >> Signed-off-by: Kees Cook <keescook@chromium.org>
> >
> > Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> 
> Acked-by: Michael Ellerman <mpe@ellerman.id.au>

Thanks! Should I take this via my tree, or do you want to take it via
ppc?

-Kees

-- 
Kees Cook