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Message-ID: <202311301304.28F0C52BA@keescook>
Date: Thu, 30 Nov 2023 13:07:13 -0800
From: Kees Cook <keescook@...omium.org>
To: "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: Masahiro Yamada <masahiroy@...nel.org>,
Nathan Chancellor <nathan@...nel.org>,
Nick Desaulniers <ndesaulniers@...gle.com>,
Nicolas Schier <nicolas@...sle.eu>,
linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] init: Kconfig: Disable -Wstringop-overflow for
GCC-11
On Thu, Nov 30, 2023 at 02:52:10PM -0600, Gustavo A. R. Silva wrote:
> -Wstringop-overflow is buggy in GCC-11. Therefore, we should disable
Can you add some links for this? For example, maybe this?
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97490
Or discussions from -next builds?
> this option specifically for that compiler version. To achieve this,
> we introduce a new configuration option: GCC11_NO_STRINGOP_OVERFLOW.
>
> The compiler option related to string operation overflow is now managed
> under configuration CC_STRINGOP_OVERFLOW. This option is enabled by
> default for all other versions of GCC that support it.
>
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
But yeah, let's get this landed to keep new warnings from appearing...
Reviewed-by: Kees Cook <keescook@...omium.org>
> ---
> Makefile | 4 +++-
> init/Kconfig | 12 ++++++++++++
> 2 files changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/Makefile b/Makefile
> index 2cfd71ae3a86..8adc611fb611 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -982,7 +982,9 @@ NOSTDINC_FLAGS += -nostdinc
> # perform bounds checking.
> KBUILD_CFLAGS += $(call cc-option, -fstrict-flex-arrays=3)
>
> -KBUILD_CFLAGS += $(call cc-option, -Wstringop-overflow)
> +#Currently, disable -Wstringop-overflow for GCC 11, globally.
> +KBUILD_CFLAGS-$(CONFIG_CC_NO_STRINGOP_OVERFLOW) += $(call cc-option, -Wno-stringop-overflow)
> +KBUILD_CFLAGS-$(CONFIG_CC_STRINGOP_OVERFLOW) += $(call cc-option, -Wstringop-overflow)
>
> # disable invalid "can't wrap" optimizations for signed / pointers
> KBUILD_CFLAGS += -fno-strict-overflow
> diff --git a/init/Kconfig b/init/Kconfig
> index 9ffb103fc927..aaaa99a5d2a9 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -876,6 +876,18 @@ config CC_NO_ARRAY_BOUNDS
> bool
> default y if CC_IS_GCC && GCC_VERSION >= 110000 && GCC11_NO_ARRAY_BOUNDS
>
> +# Currently, disable -Wstringop-overflow for GCC 11, globally.
> +config GCC11_NO_STRINGOP_OVERFLOW
> + def_bool y
> +
> +config CC_NO_STRINGOP_OVERFLOW
> + bool
> + default y if CC_IS_GCC && GCC_VERSION >= 110000 && GCC_VERSION < 120000 && GCC11_NO_STRINGOP_OVERFLOW
> +
> +config CC_STRINGOP_OVERFLOW
> + bool
> + default y if CC_IS_GCC && !CC_NO_STRINGOP_OVERFLOW
> +
> #
> # For architectures that know their GCC __int128 support is sound
> #
> --
> 2.34.1
>
--
Kees Cook
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