linux-hardening - Re: [PATCH] sata_fsl: Use struct

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Date:   Thu, 18 Nov 2021 15:55:17 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>
Cc:     Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org,
        linux-ide@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] sata_fsl: Use struct_group() for memcpy() region

On Fri, Nov 19, 2021 at 08:52:36AM +0900, Damien Le Moal wrote:
> On 2021/11/19 8:39, Kees Cook wrote:
> > On Fri, Nov 19, 2021 at 08:17:14AM +0900, Damien Le Moal wrote:
> >> On 2021/11/19 3:38, Kees Cook wrote:
> >>> In preparation for FORTIFY_SOURCE performing compile-time and run-time
> >>> field bounds checking for memcpy(), memmove(), and memset(), avoid
> >>> intentionally writing across neighboring fields.
> >>>
> >>> Use struct_group() in struct command_desc around members acmd and fill,
> >>> so they can be referenced together. This will allow memset(), memcpy(),
> >>> and sizeof() to more easily reason about sizes, improve readability,
> >>> and avoid future warnings about writing beyond the end of acmd:
> >>>
> >>> In function 'fortify_memset_chk',
> >>>     inlined from 'sata_fsl_qc_prep' at drivers/ata/sata_fsl.c:534:3:
> >>> ./include/linux/fortify-string.h:199:4: warning: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Wattribute-warning]
> >>>   199 |    __write_overflow_field();
> >>>       |    ^~~~~~~~~~~~~~~~~~~~~~~~
> >>>
> >>> Signed-off-by: Kees Cook <keescook@...omium.org>
> >>
> >> This lacks some context with regard to FORTIFY_SOURCE and struct_group(). Is
> >> that already in 5.16 ? It sounds like it is not. Do you want a ack ? Or do you
> >> want me to queue this up for 5.17 ?
> > 
> > Ah yes, some details are here in the earlier "big" series cover letter
> > here:
> > https://lore.kernel.org/linux-hardening/20210818060533.3569517-1-keescook@chromium.org/
> > 
> > One of the requests from earlier review was to split it up for separate
> > trees for the maintainers that wanted to take stuff via their trees
> > directly.
> > 
> > The new helpers are landed as of v5.16-rc1, so it can go either way, but
> > given that the merge window is closed, I would expect this to be for
> > v5.17.
> > 
> > I am happy to to carry it in my fortify topic branch that I'm expecting
> > to send for 5.17, but totally up to you. Some folks like to take these
> > changes via their trees, others would rather not be bothered with it. :)
> 
> OK. Since it looks like the compilation warning will trigger only when your big
> series land in 5.17, I will queue this in for-5.17 (still need to create than
> one). Is it ok with you ?

Yup, that works for me.

Thanks!

-Kees

-- 
Kees Cook