linux-kernel - Re: [PATCH v2 2/2] hardening: Enable i386 FORTIFY

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Message-ID: <20250308091911.GB707537@ax162>
Date: Sat, 8 Mar 2025 10:19:11 +0100
From: Nathan Chancellor <nathan@...nel.org>
To: Kees Cook <kees@...nel.org>
Cc: Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>, linux-kernel@...r.kernel.org,
	x86@...nel.org, linux-hardening@...r.kernel.org,
	linux-security-module@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH v2 2/2] hardening: Enable i386 FORTIFY_SOURCE on Clang 16+

On Fri, Mar 07, 2025 at 08:29:26PM -0800, Kees Cook wrote:
> The i386 regparm bug exposed with FORTIFY_SOURCE with Clang was fixed
> in Clang 16[1].
> 
> Link: https://github.com/llvm/llvm-project/commit/c167c0a4dcdb998affb2756ce76903a12f7d8ca5 [1]
> Signed-off-by: Kees Cook <kees@...nel.org>

Reviewed-by: Nathan Chancellor <nathan@...nel.org>

> ---
>  arch/x86/Makefile          | 2 +-
>  security/Kconfig.hardening | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/Makefile b/arch/x86/Makefile
> index d25ed25fb7d9..917459d1ad40 100644
> --- a/arch/x86/Makefile
> +++ b/arch/x86/Makefile
> @@ -137,7 +137,7 @@ ifeq ($(CONFIG_X86_32),y)
>          include $(srctree)/arch/x86/Makefile_32.cpu
>          KBUILD_CFLAGS += $(cflags-y)
>  
> -    ifeq ($(CONFIG_CC_IS_CLANG),y)
> +    ifneq ($(call clang-min-version, 160000),y)
>          # temporary until string.h is fixed
>          KBUILD_CFLAGS += -ffreestanding
>      endif
> diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening
> index 23ffb0d7c845..c17366ce8224 100644
> --- a/security/Kconfig.hardening
> +++ b/security/Kconfig.hardening
> @@ -286,7 +286,7 @@ config FORTIFY_SOURCE
>  	bool "Harden common str/mem functions against buffer overflows"
>  	depends on ARCH_HAS_FORTIFY_SOURCE
>  	# https://github.com/llvm/llvm-project/issues/53645
> -	depends on !CC_IS_CLANG || !X86_32
> +	depends on !X86_32 || !CC_IS_CLANG || CLANG_VERSION >= 160000
>  	help
>  	  Detect overflows of buffers in common string and memory functions
>  	  where the compiler can determine and validate the buffer sizes.
> -- 
> 2.34.1
>