[PATCH 4.4-cip 07/23] ubsan: fix tree-wide -Wmaybe-uninitialized false positives

Ben Hutchings <ben.hutchings@...>

From: Andrey Ryabinin <aryabinin@...>

commit dde5cf39d4d2cce71f2997c37210dd624d0e4bf6 upstream.

-fsanitize=* options makes GCC less smart than usual and increase number
of 'maybe-uninitialized' false-positives. So this patch does two things:

* Add -Wno-maybe-uninitialized to CFLAGS_UBSAN which will disable all
such warnings for instrumented files.

* Remove CONFIG_UBSAN_SANITIZE_ALL from all[yes|mod]config builds. So
the all[yes|mod]config build goes without -fsanitize=* and still with

Signed-off-by: Andrey Ryabinin <aryabinin@...>
Reported-by: Fengguang Wu <fengguang.wu@...>
Signed-off-by: Andrew Morton <akpm@...>
Signed-off-by: Linus Torvalds <torvalds@...>
Signed-off-by: Ben Hutchings <ben.hutchings@...>
lib/Kconfig.ubsan | 5 +++++
scripts/Makefile.ubsan | 4 ++++
2 files changed, 9 insertions(+)

diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan
index e07c1ba9ba13..39494af9a84a 100644
--- a/lib/Kconfig.ubsan
+++ b/lib/Kconfig.ubsan
@@ -13,6 +13,11 @@ config UBSAN_SANITIZE_ALL
bool "Enable instrumentation for the entire kernel"
depends on UBSAN
+ # We build with -Wno-maybe-uninitilzed, but we still want to
+ # use -Wmaybe-uninitilized in allmodconfig builds.
+ # So dependsy bellow used to disable this option in allmodconfig
+ depends on !COMPILE_TEST
default y
This option activates instrumentation for the entire kernel.
diff --git a/scripts/Makefile.ubsan b/scripts/Makefile.ubsan
index 8ab68679cfb5..77ce538268b5 100644
--- a/scripts/Makefile.ubsan
+++ b/scripts/Makefile.ubsan
@@ -14,4 +14,8 @@ ifdef CONFIG_UBSAN
CFLAGS_UBSAN += $(call cc-option, -fsanitize=alignment)
+ # -fsanitize=* options makes GCC less smart than usual and
+ # increase number of 'maybe-uninitialized false-positives
+ CFLAGS_UBSAN += $(call cc-option, -Wno-maybe-uninitialized)

Ben Hutchings
Software Developer, Codethink Ltd.

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