Re: [PATCH 4/5] Makefile: Enable -Warray-bounds

[Guenter Roeck]

On Wed, Aug 18, 2021 at 01:11:17AM -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@xxxxxxxx>
> Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx>
> Cc: linux-kbuild@xxxxxxxxxxxxxxx
> Co-developed-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
> Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
>  Makefile | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/Makefile b/Makefile
> index a4aca01a4835..af22b83cede7 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1072,7 +1072,6 @@ 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 += -Wno-array-bounds
>  KBUILD_CFLAGS += $(call cc-disable-warning, stringop-overflow)
>  
>  # Another good warning that we'll want to enable eventually

alpha:defconfig:

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);


xtensa:allmodconfig:
--------------
Error log:
In file included from include/linux/uaccess.h:11,
                 from include/linux/sched/task.h:11,
                 from arch/xtensa/kernel/process.c:21:
arch/xtensa/kernel/process.c: In function 'copy_thread':
arch/xtensa/kernel/process.c:262:52: error: array subscript 53 is above array bounds of 'long unsigned int[16]'