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From: Kees Cook <keescook@chromium.org>
To: Guenter Roeck <linux@roeck-us.net>
Cc: linux-kernel@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
	Masahiro Yamada <masahiroy@kernel.org>,
	linux-kbuild@vger.kernel.org,
	"Gustavo A . R . Silva" <gustavoars@kernel.org>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	Keith Packard <keithp@keithp.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Daniel Vetter <daniel.vetter@ffwll.ch>,
	clang-built-linux@googlegroups.com,
	linux-hardening@vger.kernel.org
Subject: Re: [PATCH v3 4/5] Makefile: Enable -Warray-bounds
Date: Tue, 31 Aug 2021 10:46:01 -0700	[thread overview]
Message-ID: <202108311042.FFE1818D@keescook> (raw)
In-Reply-To: <20210831043128.GA2749311@roeck-us.net>

On Mon, Aug 30, 2021 at 09:31:28PM -0700, Guenter Roeck wrote:
> On Fri, Aug 27, 2021 at 09:30:14AM -0700, Kees Cook wrote:
> > With the recent fixes for flexible arrays and expanded FORTIFY_SOURCE
> > coverage, it is now possible to enable -Warray-bounds. Since both
> > GCC and Clang include -Warray-bounds in -Wall, we just need to stop
> > disabling it.
> > 
> > Cc: Arnd Bergmann <arnd@arndb.de>
> > Cc: Masahiro Yamada <masahiroy@kernel.org>
> > Cc: linux-kbuild@vger.kernel.org
> > Co-developed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> > ---
> >  Makefile | 1 -
> >  1 file changed, 1 deletion(-)
> > 
> > diff --git a/Makefile b/Makefile
> > index e4f5895badb5..8e7e73a642e2 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -995,7 +995,6 @@ KBUILD_CFLAGS += $(call cc-disable-warning, stringop-truncation)
> >  
> >  # We'll want to enable this eventually, but it's not going away for 5.7 at least
> >  KBUILD_CFLAGS += $(call cc-disable-warning, zero-length-bounds)
> > -KBUILD_CFLAGS += $(call cc-disable-warning, array-bounds)
> >  KBUILD_CFLAGS += $(call cc-disable-warning, stringop-overflow)
> >  
> 
> This patch causes 'alpha' builds to fail when trying to build an image with
> gcc 11.2.
> 
> In file included from include/linux/string.h:20,
>                  from include/linux/bitmap.h:11,
>                  from include/linux/cpumask.h:12,
>                  from include/linux/smp.h:13,
>                  from include/linux/lockdep.h:14,
>                  from include/linux/spinlock.h:63,
>                  from include/linux/mmzone.h:8,
>                  from include/linux/gfp.h:6,
>                  from include/linux/mm.h:10,
>                  from include/linux/pagemap.h:8,
>                  from arch/alpha/mm/init.c:10:
> In function '__memset',
>     inlined from '__bad_pagetable' at arch/alpha/mm/init.c:79:2:
> arch/alpha/include/asm/string.h:37:32: error: '__builtin_memset' offset [0, 8191] is out of the bounds [0, 0] [-Werror=array-bounds]
>    37 |                         return __builtin_memset(s, c, n);
>       |                                ^~~~~~~~~~~~~~~~~~~~~~~~~
> In function '__memset',
>     inlined from '__bad_page' at arch/alpha/mm/init.c:86:2:
> arch/alpha/include/asm/string.h:37:32: error: '__builtin_memset' offset [0, 8191] is out of the bounds [0, 0] [-Werror=array-bounds]
>    37 |                         return __builtin_memset(s, c, n);
>       |                                ^~~~~~~~~~~~~~~~~~~~~~~~~
> In function '__memset',
>     inlined from 'paging_init' at arch/alpha/mm/init.c:256:2:
> arch/alpha/include/asm/string.h:37:32: error: '__builtin_memset' offset [0, 8191] is out of the bounds [0, 0] [-Werror=array-bounds]
>    37 |                         return __builtin_memset(s, c, n);
> 
> Seen in next-20210830.

Ah-ha, thanks for the report! I didn't see this in my builds -- what
config target did you use for this?

Looks like GCC isn't happy about an unsigned long->void * conversion
here...

include/asm/page.h:#define PAGE_OFFSET          0xfffffc0000000000UL
...
include/uapi/asm/setup.h:#define KERNEL_START_PHYS      0x1000000 /* required: Wildfire/Titan/Marvel */
include/uapi/asm/setup.h:#define EMPTY_PGT (PAGE_OFFSET+KERNEL_START_PHYS+0x04000)
...
mm/init.c:      memset((void *) EMPTY_PGT, 0, PAGE_SIZE);

I'll try to figure out the right annotations to fix this...

-- 
Kees Cook

  reply	other threads:[~2021-08-31 17:46 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-27 16:30 [PATCH v3 0/5] Enable -Warray-bounds and -Wzero-length-bounds Kees Cook
2021-08-27 16:30 ` [PATCH v3 1/5] stddef: Introduce DECLARE_FLEX_ARRAY() helper Kees Cook
2021-08-27 16:30 ` [PATCH v3 2/5] treewide: Replace open-coded flex arrays in unions Kees Cook
2021-08-28  7:51   ` Vincent MAILHOL
2021-08-27 16:30 ` [PATCH v3 3/5] treewide: Replace 0-element memcpy() destinations with flexible arrays Kees Cook
2021-08-27 16:30 ` [PATCH v3 4/5] Makefile: Enable -Warray-bounds Kees Cook
2021-08-31  4:31   ` Guenter Roeck
2021-08-31 17:46     ` Kees Cook [this message]
2021-08-31 19:40       ` Guenter Roeck
2021-08-31 20:18         ` Kees Cook
2021-08-31 20:49           ` Guenter Roeck
2021-08-27 16:30 ` [PATCH v3 5/5] Makefile: Enable -Wzero-length-bounds Kees Cook
2021-08-30 18:44 ` [PATCH v3 0/5] Enable -Warray-bounds and -Wzero-length-bounds Nathan Chancellor
2021-08-30 20:12   ` Kees Cook
2021-08-30 20:16   ` Kees Cook
2021-08-30 22:34     ` Nathan Chancellor

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