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Date:   Wed, 08 Jun 2022 17:39:36 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Linus Torvalds <torvalds@linux-foundation.org>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Shawn Guo <shawnguo@kernel.org>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Fabio Estevam <festevam@gmail.com>,
        David Howells <dhowells@redhat.com>
CC:     Sven Schnelle <svens@linux.ibm.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Alexander Gordeev <agordeev@linux.ibm.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] s390: disable -Warray-bounds
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On June 8, 2022 4:59:29 PM PDT, Linus Torvalds <torvalds@linux-foundation=
=2Eorg> wrote:
>On Wed, Jun 8, 2022 at 2:33 PM Kees Cook <keescook@chromium=2Eorg> wrote:
>>
>> I and others have been working through a bunch of them, though yes,
>> they're not all fixed yet=2E I've been trying to track it here[1], but
>> many of those fixes are only in -next=2E
>
>Hmm=2E Even with that disabled, I get a few warnings I *really* would
>want to get rid of=2E

Yup! :)

>
>The one in ipuv3-crtc=2Ec seems valid about "address used as boolean is
>always true"=2E
>
>The 'dangling-pointer' warning does seem interesting, but not when the
>compiler does as bad a job as gcc seems to do=2E
>
>See the attached patch for
>
> (a) make the s390 "use -Wno-array-bounds for gcc-12" be generic
>
> (b) fix the ipuv3-crtc=2Ec one=2E IMX people?
>
> (c) disable -Wdangling-pointer entirely for now

I'll take a look; thanks! Should I send them back as a pull request?

>but that still leaves the netfs_i_context games, which gcc-12 is very
>unhappy about:

Yeah=2E Happily, this has already been solved, but it looks like David did=
n't do a pull yet for it?

https://git=2Ekernel=2Eorg/pub/scm/linux/kernel/git/dhowells/linux-fs=2Egi=
t/log/?h=3Dfscache-next


>I'd like to use something more surgical than
>CONFIG_CC_NO_ARRAY_BOUNDS, but considering the s390 issues, it may not
>even be worth it=2E Kees, just how far away are we from that being ok on
>x86-64?

For gcc's UBSAN_SHIFT (I typoed this in my first reply) bug, netdev has be=
en moving it to W=3D1 builds on a per-source basis for the moment:

https://git=2Ekernel=2Eorg/linus/e95032988053c17baf6c7e27024f5103a19a5f4a

Some discussion:
https://lore=2Ekernel=2Eorg/lkml/202205231229=2ECF6B8471@keescook/

Perhaps these could be even more carefully limited to GCC 12 only, using t=
he Kconfig you suggested?

-Kees

--=20
Kees Cook