linux-kernel - [PATCH 3/4] ubsan: Force -Wno-maybe-uninitialized only for GCC

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Date:   Fri,  2 Oct 2020 15:15:26 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nathan Chancellor <natechancellor@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        George Popescu <georgepope@...roid.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Peter Oberparleiter <oberpar@...ux.ibm.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        clang-built-linux@...glegroups.com, linux-kbuild@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 3/4] ubsan: Force -Wno-maybe-uninitialized only for GCC

Clang handles 'maybe-uninitialized' better in the face of using UBSAN,
so do not make this universally disabled for UBSAN builds.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 lib/Kconfig.ubsan      | 6 ++++++
 scripts/Makefile.ubsan | 6 +++---
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan
index aeb2cdea0b94..1fc07f936e06 100644
--- a/lib/Kconfig.ubsan
+++ b/lib/Kconfig.ubsan
@@ -36,6 +36,12 @@ config UBSAN_KCOV_BROKEN
 	  See https://bugs.llvm.org/show_bug.cgi?id=45831 for the status
 	  in newer releases.
 
+config UBSAN_DISABLE_MAYBE_UNINITIALIZED
+	def_bool CC_IS_GCC
+	help
+	  -fsanitize=* options makes GCC less smart than usual and
+	  increases the number of 'maybe-uninitialized' false-positives.
+
 config CC_HAS_UBSAN_BOUNDS
 	def_bool $(cc-option,-fsanitize=bounds)
 
diff --git a/scripts/Makefile.ubsan b/scripts/Makefile.ubsan
index 72862da47baf..c5ef6bac09d4 100644
--- a/scripts/Makefile.ubsan
+++ b/scripts/Makefile.ubsan
@@ -1,8 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0
 
-# -fsanitize=* options makes GCC less smart than usual and
-# increases the number of 'maybe-uninitialized' false-positives.
-ubsan-cflags-$(CONFIG_UBSAN) += $(call cc-disable-warning, maybe-uninitialized)
+# The "maybe-uninitialized" warning can be very noisy.
+ubsan-cflags-$(CONFIG_UBSAN_DISABLE_MAYBE_UNINITIALIZED) += \
+						$(call cc-disable-warning, maybe-uninitialized)
 
 # Enable available and selected UBSAN features.
 ubsan-cflags-$(CONFIG_UBSAN_ALIGNMENT)		+= -fsanitize=alignment
-- 
2.25.1