Re: [PATCH] powerpc/signal32: Use struct_group() to zero spe regs

On Wed, Nov 24, 2021 at 11:08:25AM +1100, Michael Ellerman wrote:

Kees Cook [off-list ref] writes:

quoted

On Mon, Nov 22, 2021 at 04:43:36PM +1100, Michael Ellerman wrote:

quoted

LEROY Christophe [off-list ref] writes:

quoted

Le 18/11/2021 à 21:36, Kees Cook a écrit :

quoted

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 <redacted>
Signed-off-by: Kees Cook <redacted>

Reviewed-by: Christophe Leroy <redacted>

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?

I don't mind. If it's easier for you to take it as part of an existing
series then do that, otherwise I can pick it up.

Most of the other patches are going via other maintainers, so I'd love
it if ppc could snag this one too. :)

Thanks!

-Kees

-- 
Kees Cook