[PATCH v2 2/7] ubsan: Move cc-option tests into Kconfig

Kees Cook
2020-12-03T00:45:50Z

Instead of doing if/endif blocks with cc-option calls in the UBSAN
Makefile, move all the tests into Kconfig and use the Makefile to
collect the results.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/lkml/CAHk-=wjPasyJrDuwDnpHJS2TuQfExwe=px-SzLeN8GFMAQJPmQ@mail.gmail.com/
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
lib/Kconfig.ubsan | 61 +++++++++++++++++++++++++++++++++++++++---
scripts/Makefile.ubsan | 45 +++++++++++--------------------
2 files changed, 73 insertions(+), 33 deletions(-)

diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan
index d8d4d6557b80..05147112b355 100644
--- a/lib/Kconfig.ubsan
+++ b/lib/Kconfig.ubsan
@@ -36,10 +36,17 @@ config UBSAN_KCOV_BROKEN
See https://bugs.llvm.org/show_bug.cgi?id=45831 for the status
in newer releases.

+config CC_HAS_UBSAN_BOUNDS
+ def_bool $(cc-option,-fsanitize=bounds)
+
+config CC_HAS_UBSAN_ARRAY_BOUNDS
+ def_bool $(cc-option,-fsanitize=array-bounds)
+
config UBSAN_BOUNDS
bool "Perform array index bounds checking"
default UBSAN
depends on !UBSAN_KCOV_BROKEN
+ depends on CC_HAS_UBSAN_ARRAY_BOUNDS || CC_HAS_UBSAN_BOUNDS
help
This option enables detection of directly indexed out of bounds
array accesses, where the array size is known at compile time.
@@ -47,15 +54,30 @@ config UBSAN_BOUNDS
to the {str,mem}*cpy() family of functions (that is addressed
by CONFIG_FORTIFY_SOURCE).

+config UBSAN_ONLY_BOUNDS
+ def_bool CC_HAS_UBSAN_BOUNDS && !CC_HAS_UBSAN_ARRAY_BOUNDS
+ depends on UBSAN_BOUNDS
+ help
+ This is a weird case: Clang's -fsanitize=bounds includes
+ -fsanitize=local-bounds, but it's trapping-only, so for
+ Clang, we must use -fsanitize=array-bounds when we want
+ traditional array bounds checking enabled. For GCC, we
+ want -fsanitize=bounds.
+
+config UBSAN_ARRAY_BOUNDS
+ def_bool CC_HAS_UBSAN_ARRAY_BOUNDS
+ depends on UBSAN_BOUNDS
+
config UBSAN_LOCAL_BOUNDS
bool "Perform array local bounds checking"
depends on UBSAN_TRAP
- depends on CC_IS_CLANG
depends on !UBSAN_KCOV_BROKEN
+ depends on $(cc-option,-fsanitize=local-bounds)
help
This option enables -fsanitize=local-bounds which traps when an
- exception/error is detected. Therefore, it should be enabled only
- if trapping is expected.
+ exception/error is detected. Therefore, it may only be enabled
+ with CONFIG_UBSAN_TRAP.
+
Enabling this option detects errors due to accesses through a
pointer that is derived from an object of a statically-known size,
where an added offset (which may not be known statically) is
@@ -69,6 +91,38 @@ config UBSAN_MISC
own Kconfig options. Disable this if you only want to have
individually selected checks.

+config UBSAN_SHIFT
+ def_bool UBSAN_MISC
+ depends on $(cc-option,-fsanitize=shift)
+
+config UBSAN_DIV_ZERO
+ def_bool UBSAN_MISC
+ depends on $(cc-option,-fsanitize=integer-divide-by-zero)
+
+config UBSAN_UNREACHABLE
+ def_bool UBSAN_MISC
+ depends on $(cc-option,-fsanitize=unreachable)
+
+config UBSAN_SIGNED_OVERFLOW
+ def_bool UBSAN_MISC
+ depends on $(cc-option,-fsanitize=signed-integer-overflow)
+
+config UBSAN_UNSIGNED_OVERFLOW
+ def_bool UBSAN_MISC
+ depends on $(cc-option,-fsanitize=unsigned-integer-overflow)
+
+config UBSAN_OBJECT_SIZE
+ def_bool UBSAN_MISC
+ depends on $(cc-option,-fsanitize=object-size)
+
+config UBSAN_BOOL
+ def_bool UBSAN_MISC
+ depends on $(cc-option,-fsanitize=bool)
+
+config UBSAN_ENUM
+ def_bool UBSAN_MISC
+ depends on $(cc-option,-fsanitize=enum)
+
config UBSAN_SANITIZE_ALL
bool "Enable instrumentation for the entire kernel"
depends on ARCH_HAS_UBSAN_SANITIZE_ALL
@@ -85,6 +139,7 @@ config UBSAN_ALIGNMENT
bool "Enable checks for pointers alignment"
default !HAVE_EFFICIENT_UNALIGNED_ACCESS
depends on !UBSAN_TRAP
+ depends on $(cc-option,-fsanitize=alignment)
help
This option enables the check of unaligned memory accesses.
Enabling this option on architectures that support unaligned
diff --git a/scripts/Makefile.ubsan b/scripts/Makefile.ubsan
index c18fecc53605..0e53a93e8f15 100644
--- a/scripts/Makefile.ubsan
+++ b/scripts/Makefile.ubsan
@@ -1,33 +1,18 @@
# SPDX-License-Identifier: GPL-2.0

-export CFLAGS_UBSAN :=
+# Enable available and selected UBSAN features.
+ubsan-cflags-$(CONFIG_UBSAN_ALIGNMENT) += -fsanitize=alignment
+ubsan-cflags-$(CONFIG_UBSAN_ONLY_BOUNDS) += -fsanitize=bounds
+ubsan-cflags-$(CONFIG_UBSAN_ARRAY_BOUNDS) += -fsanitize=array-bounds
+ubsan-cflags-$(CONFIG_UBSAN_LOCAL_BOUNDS) += -fsanitize=local-bounds
+ubsan-cflags-$(CONFIG_UBSAN_SHIFT) += -fsanitize=shift
+ubsan-cflags-$(CONFIG_UBSAN_DIV_ZERO) += -fsanitize=integer-divide-by-zero
+ubsan-cflags-$(CONFIG_UBSAN_UNREACHABLE) += -fsanitize=unreachable
+ubsan-cflags-$(CONFIG_UBSAN_SIGNED_OVERFLOW) += -fsanitize=signed-integer-overflow
+ubsan-cflags-$(CONFIG_UBSAN_UNSIGNED_OVERFLOW) += -fsanitize=unsigned-integer-overflow
+ubsan-cflags-$(CONFIG_UBSAN_OBJECT_SIZE) += -fsanitize=object-size
+ubsan-cflags-$(CONFIG_UBSAN_BOOL) += -fsanitize=bool
+ubsan-cflags-$(CONFIG_UBSAN_ENUM) += -fsanitize=enum
+ubsan-cflags-$(CONFIG_UBSAN_TRAP) += -fsanitize-undefined-trap-on-error

-ifdef CONFIG_UBSAN_ALIGNMENT
- CFLAGS_UBSAN += $(call cc-option, -fsanitize=alignment)
-endif
-
-ifdef CONFIG_UBSAN_BOUNDS
- ifdef CONFIG_CC_IS_CLANG
- CFLAGS_UBSAN += -fsanitize=array-bounds
- else
- CFLAGS_UBSAN += $(call cc-option, -fsanitize=bounds)
- endif
-endif
-
-ifdef CONFIG_UBSAN_LOCAL_BOUNDS
- CFLAGS_UBSAN += -fsanitize=local-bounds
-endif
-
-ifdef CONFIG_UBSAN_MISC
- CFLAGS_UBSAN += $(call cc-option, -fsanitize=shift)
- CFLAGS_UBSAN += $(call cc-option, -fsanitize=integer-divide-by-zero)
- CFLAGS_UBSAN += $(call cc-option, -fsanitize=unreachable)
- CFLAGS_UBSAN += $(call cc-option, -fsanitize=signed-integer-overflow)
- CFLAGS_UBSAN += $(call cc-option, -fsanitize=object-size)
- CFLAGS_UBSAN += $(call cc-option, -fsanitize=bool)
- CFLAGS_UBSAN += $(call cc-option, -fsanitize=enum)
-endif
-
-ifdef CONFIG_UBSAN_TRAP
- CFLAGS_UBSAN += $(call cc-option, -fsanitize-undefined-trap-on-error)
-endif
+export CFLAGS_UBSAN := $(ubsan-cflags-y)
--
2.25.1