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Date:   Mon, 26 Dec 2022 17:32:28 -0800
From:   Kees Cook <kees@kernel.org>
To:     Guenter Roeck <linux@roeck-us.net>
CC:     Linus Torvalds <torvalds@linux-foundation.org>,
        Jaegeuk Kim <jaegeuk@kernel.org>, Chao Yu <chao@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        Peter Zijlstra <peterz@infradead.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Kees Cook <keescook@chromium.org>
Subject: Re: Linux 6.2-rc1
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On December 26, 2022 4:29:41 PM PST, Guenter Roeck <linux@roeck-us=2Enet> w=
rote:
>On Mon, Dec 26, 2022 at 01:03:59PM -0800, Kees Cook wrote:
>> On December 26, 2022 12:56:29 PM PST, Linus Torvalds <torvalds@linux-fo=
undation=2Eorg> wrote:
>> >On Mon, Dec 26, 2022 at 11:52 AM Guenter Roeck <linux@roeck-us=2Enet> =
wrote:
>> >>
>> >> fs/f2fs/inline=2Ec: In function 'f2fs_move_inline_dirents':
>> >> include/linux/fortify-string=2Eh:59:33: error: '__builtin_memset' po=
inter overflow between offset [28, 898293814] and size [-898293787, -1] [-W=
error=3Darray-bounds]
>> >> fs/f2fs/inline=2Ec:430:9: note: in expansion of macro 'memset'
>> >>   430 |         memset(dst=2Ebitmap + src=2Enr_bitmap, 0, dst=2Enr_b=
itmap - src=2Enr_bitmap);
>> >>       |         ^~~~~~
>> >
>> >Well, that's unfortunate=2E
>>=20
>> I'll look into this=2E
>>=20
>
>I did some more testing=2E The problem is seen with gcc 11=2E3=2E0, but n=
ot with
>gcc 12=2E2=2E0 nor with gcc 10=2E3=2E0=2E

That's what I'd expect: 10 didn't have variable range tracking wired up to=
 -Warray-bounds, 11 does, and we disable -Warray-bounds on 12 because of 3 =
separate 12-only GCC bugs=2E

> gcc bug ? Should I switch to gcc 12=2E2=2E0 for
>powerpc when build testing the latest kernel ?

Sure? But that'll just hide it=2E I suspect GCC has found a way for dst=2E=
nr_bitmap to be compile-time 27, so the size is always negative=2E


--=20
Kees Cook