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From:   Kees Cook <keescook@chromium.org>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Kees Cook <keescook@chromium.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Ard Biesheuvel <ardb@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Michal Marek <michal.lkml@markovi.net>,
        Nathan Chancellor <natechancellor@gmail.com>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Marco Elver <elver@google.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Dmitry Vyukov <dvyukov@google.com>,
        George Popescu <georgepope@android.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Peter Oberparleiter <oberpar@linux.ibm.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        clang-built-linux@googlegroups.com, linux-kbuild@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH 3/4] ubsan: Force -Wno-maybe-uninitialized only for GCC
Date:   Fri,  2 Oct 2020 15:15:26 -0700
Message-Id: <20201002221527.177500-4-keescook@chromium.org>
In-Reply-To: <20201002221527.177500-1-keescook@chromium.org>
References: <20201002221527.177500-1-keescook@chromium.org>
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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@chromium.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