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Commit 0d4d3b41 authored by Kees Cook's avatar Kees Cook Committed by Nick Desaulniers
Browse files

UPSTREAM: hardening: Remove Clang's enable flag for -ftrivial-auto-var-init=zero 



Now that Clang's -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang
option is no longer required, remove it from the command line. Clang 16
and later will warn when it is used, which will cause Kconfig to think
it can't use -ftrivial-auto-var-init=zero at all. Check for whether it
is required and only use it when so.

Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: linux-kbuild@vger.kernel.org
Cc: llvm@lists.linux.dev
Cc: stable@vger.kernel.org
Fixes: f02003c860d9 ("hardening: Avoid harmless Clang option under CONFIG_INIT_STACK_ALL_ZERO")
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
(cherry picked from commit 607e57c6c62c00965ae276902c166834ce73014a)
Change-Id: I30ecd0e5226852b7d5ee12c44c346ac79051a671
Signed-off-by: default avatarNathan Chancellor <nathan@kernel.org>
parent 9267f980

Makefile

+2 −2
Original line number Diff line number Diff line
@@ -811,8 +811,8 @@ endif 
# Initialize all stack variables with a zero value.

ifdef CONFIG_INIT_STACK_ALL_ZERO

KBUILD_CFLAGS	+= -ftrivial-auto-var-init=zero

ifdef CONFIG_CC_IS_CLANG

# https://bugs.llvm.org/show_bug.cgi?id=45497

ifdef CONFIG_CC_HAS_AUTO_VAR_INIT_ZERO_ENABLER

# https://github.com/llvm/llvm-project/issues/44842

KBUILD_CFLAGS	+= -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang

endif

endif

security/Kconfig.hardening

+10 −4
Original line number Diff line number Diff line
@@ -22,11 +22,17 @@ menu "Memory initialization" 
config CC_HAS_AUTO_VAR_INIT_PATTERN

	def_bool $(cc-option,-ftrivial-auto-var-init=pattern)



config CC_HAS_AUTO_VAR_INIT_ZERO

	# GCC ignores the -enable flag, so we can test for the feature with

	# a single invocation using the flag, but drop it as appropriate in

	# the Makefile, depending on the presence of Clang.

config CC_HAS_AUTO_VAR_INIT_ZERO_BARE

	def_bool $(cc-option,-ftrivial-auto-var-init=zero)



config CC_HAS_AUTO_VAR_INIT_ZERO_ENABLER

	# Clang 16 and later warn about using the -enable flag, but it

	# is required before then.

	def_bool $(cc-option,-ftrivial-auto-var-init=zero -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang)

	depends on !CC_HAS_AUTO_VAR_INIT_ZERO_BARE



config CC_HAS_AUTO_VAR_INIT_ZERO

	def_bool CC_HAS_AUTO_VAR_INIT_ZERO_BARE || CC_HAS_AUTO_VAR_INIT_ZERO_ENABLER



choice

	prompt "Initialize kernel stack variables at function entry"