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557f8c582a
In order to mitigate unexpected signed wrap-around[1], bring back the
signed integer overflow sanitizer. It was removed in commit 6aaa31aeb9cf
("ubsan: remove overflow checks") because it was effectively a no-op
when combined with -fno-strict-overflow (which correctly changes signed
overflow from being "undefined" to being explicitly "wrap around").
Compilers are adjusting their sanitizers to trap wrap-around and to
detecting common code patterns that should not be instrumented
(e.g. "var + offset < var"). Prepare for this and explicitly rename
the option from "OVERFLOW" to "WRAP" to more accurately describe the
behavior.
To annotate intentional wrap-around arithmetic, the helpers
wrapping_add/sub/mul_wrap() can be used for individual statements. At
the function level, the __signed_wrap attribute can be used to mark an
entire function as expecting its signed arithmetic to wrap around. For a
single object file the Makefile can use "UBSAN_SIGNED_WRAP_target.o := n"
to mark it as wrapping, and for an entire directory, "UBSAN_SIGNED_WRAP :=
n" can be used.
Additionally keep these disabled under CONFIG_COMPILE_TEST for now.
Link: https://github.com/KSPP/linux/issues/26 [1]
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Hao Luo <haoluo@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-by: Justin Stitt <justinstitt@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
19 lines
984 B
Makefile
19 lines
984 B
Makefile
# SPDX-License-Identifier: GPL-2.0
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# Enable available and selected UBSAN features.
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ubsan-cflags-$(CONFIG_UBSAN_ALIGNMENT) += -fsanitize=alignment
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ubsan-cflags-$(CONFIG_UBSAN_BOUNDS_STRICT) += -fsanitize=bounds-strict
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ubsan-cflags-$(CONFIG_UBSAN_ARRAY_BOUNDS) += -fsanitize=array-bounds
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ubsan-cflags-$(CONFIG_UBSAN_LOCAL_BOUNDS) += -fsanitize=local-bounds
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ubsan-cflags-$(CONFIG_UBSAN_SHIFT) += -fsanitize=shift
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ubsan-cflags-$(CONFIG_UBSAN_DIV_ZERO) += -fsanitize=integer-divide-by-zero
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ubsan-cflags-$(CONFIG_UBSAN_UNREACHABLE) += -fsanitize=unreachable
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ubsan-cflags-$(CONFIG_UBSAN_BOOL) += -fsanitize=bool
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ubsan-cflags-$(CONFIG_UBSAN_ENUM) += -fsanitize=enum
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ubsan-cflags-$(CONFIG_UBSAN_TRAP) += $(call cc-option,-fsanitize-trap=undefined,-fsanitize-undefined-trap-on-error)
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export CFLAGS_UBSAN := $(ubsan-cflags-y)
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ubsan-signed-wrap-cflags-$(CONFIG_UBSAN_SIGNED_WRAP) += -fsanitize=signed-integer-overflow
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export CFLAGS_UBSAN_SIGNED_WRAP := $(ubsan-signed-wrap-cflags-y)
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