Re: [PATCH] hardening: Default to INIT_STACK_ALL_ZERO if CC_HAS_AUTO_VAR_INIT_ZERO
From: Nathan Chancellor <nathan@kernel.org>
Date: 2021-09-14 15:58:18
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On 9/14/2021 3:28 AM, Will Deacon wrote:
CC_HAS_AUTO_VAR_INIT_ZERO requires a supported set of compiler options
distinct from those needed by CC_HAS_AUTO_VAR_INIT_PATTERN, Fix up
the Kconfig dependency for INIT_STACK_ALL_ZERO to test for the former
instead of the latter, as these are the options passed by the top-level
Makefile.
Cc: Kees Cook <redacted>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Gustavo A. R. Silva <gustavoars@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Fixes: dcb7c0b9461c ("hardening: Clarify Kconfig text for auto-var-init")
Signed-off-by: Will Deacon <will@kernel.org>Reviewed-by: Nathan Chancellor <nathan@kernel.org> One comment below.
quoted hunk ↗ jump to hunk
--- I just noticed this while reading the code and I suspect it doesn't really matter in practice. security/Kconfig.hardening | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening index 90cbaff86e13..341e2fdcba94 100644 --- a/security/Kconfig.hardening +++ b/security/Kconfig.hardening@@ -29,7 +29,7 @@ choice prompt "Initialize kernel stack variables at function entry" default GCC_PLUGIN_STRUCTLEAK_BYREF_ALL if COMPILE_TEST && GCC_PLUGINS default INIT_STACK_ALL_PATTERN if COMPILE_TEST && CC_HAS_AUTO_VAR_INIT_PATTERN - default INIT_STACK_ALL_ZERO if CC_HAS_AUTO_VAR_INIT_PATTERN + default INIT_STACK_ALL_ZERO if CC_HAS_AUTO_VAR_INIT_ZERO default INIT_STACK_NONE help This option enables initialization of stack variables at
While I think this change is correct in and of itself, CONFIG_INIT_STACK_ALL_ZERO is broken with GCC 12.x, as CONFIG_CC_HAS_AUTO_VAR_INIT_ZERO won't be set even though GCC now supports -ftrivial-auto-var-init=zero because GCC does not implement the -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang flag for obvious reasons ;) the cc-option call probably needs to be adjusted. Cheers, Nathan