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Since GCC 8.0 -fsanitize=signed-integer-overflow doesn't work with
-fwrapv. -fwrapv makes signed overflows defines and GCC essentially
disables ubsan checks. On GCC < 8.0 -fwrapv doesn't have influence on
-fsanitize=signed-integer-overflow setting, so it kinda works but
generates false-positves and violates uaccess rules:
lib/iov_iter.o: warning: objtool: iovec_from_user()+0x22d: call to
__ubsan_handle_add_overflow() with UACCESS enabled
Disable signed overflow checks to avoid these problems. Remove unsigned
overflow checks as well. Unsigned overflow appeared as side effect of
commit cdf8a76fda ("ubsan: move cc-option tests into Kconfig"), but it
never worked (kernel doesn't boot). And unsigned overflows are allowed by
C standard, so it just pointless.
Link: https://lkml.kernel.org/r/20210209232348.20510-1-ryabinin.a.a@gmail.com
Signed-off-by: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
173 lines
6.3 KiB
Plaintext
173 lines
6.3 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0-only
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config ARCH_HAS_UBSAN_SANITIZE_ALL
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bool
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menuconfig UBSAN
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bool "Undefined behaviour sanity checker"
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help
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This option enables the Undefined Behaviour sanity checker.
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Compile-time instrumentation is used to detect various undefined
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behaviours at runtime. For more details, see:
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Documentation/dev-tools/ubsan.rst
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if UBSAN
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config UBSAN_TRAP
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bool "On Sanitizer warnings, abort the running kernel code"
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depends on !COMPILE_TEST
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depends on $(cc-option, -fsanitize-undefined-trap-on-error)
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help
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Building kernels with Sanitizer features enabled tends to grow
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the kernel size by around 5%, due to adding all the debugging
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text on failure paths. To avoid this, Sanitizer instrumentation
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can just issue a trap. This reduces the kernel size overhead but
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turns all warnings (including potentially harmless conditions)
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into full exceptions that abort the running kernel code
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(regardless of context, locks held, etc), which may destabilize
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the system. For some system builders this is an acceptable
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trade-off.
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config UBSAN_KCOV_BROKEN
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def_bool KCOV && CC_HAS_SANCOV_TRACE_PC
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depends on CC_IS_CLANG
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depends on !$(cc-option,-Werror=unused-command-line-argument -fsanitize=bounds -fsanitize-coverage=trace-pc)
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help
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Some versions of clang support either UBSAN or KCOV but not the
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combination of the two.
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See https://bugs.llvm.org/show_bug.cgi?id=45831 for the status
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in newer releases.
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config CC_HAS_UBSAN_BOUNDS
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def_bool $(cc-option,-fsanitize=bounds)
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config CC_HAS_UBSAN_ARRAY_BOUNDS
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def_bool $(cc-option,-fsanitize=array-bounds)
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config UBSAN_BOUNDS
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bool "Perform array index bounds checking"
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default UBSAN
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depends on !UBSAN_KCOV_BROKEN
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depends on CC_HAS_UBSAN_ARRAY_BOUNDS || CC_HAS_UBSAN_BOUNDS
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help
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This option enables detection of directly indexed out of bounds
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array accesses, where the array size is known at compile time.
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Note that this does not protect array overflows via bad calls
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to the {str,mem}*cpy() family of functions (that is addressed
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by CONFIG_FORTIFY_SOURCE).
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config UBSAN_ONLY_BOUNDS
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def_bool CC_HAS_UBSAN_BOUNDS && !CC_HAS_UBSAN_ARRAY_BOUNDS
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depends on UBSAN_BOUNDS
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help
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This is a weird case: Clang's -fsanitize=bounds includes
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-fsanitize=local-bounds, but it's trapping-only, so for
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Clang, we must use -fsanitize=array-bounds when we want
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traditional array bounds checking enabled. For GCC, we
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want -fsanitize=bounds.
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config UBSAN_ARRAY_BOUNDS
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def_bool CC_HAS_UBSAN_ARRAY_BOUNDS
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depends on UBSAN_BOUNDS
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config UBSAN_LOCAL_BOUNDS
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bool "Perform array local bounds checking"
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depends on UBSAN_TRAP
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depends on !UBSAN_KCOV_BROKEN
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depends on $(cc-option,-fsanitize=local-bounds)
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help
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This option enables -fsanitize=local-bounds which traps when an
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exception/error is detected. Therefore, it may only be enabled
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with CONFIG_UBSAN_TRAP.
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Enabling this option detects errors due to accesses through a
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pointer that is derived from an object of a statically-known size,
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where an added offset (which may not be known statically) is
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out-of-bounds.
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config UBSAN_SHIFT
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bool "Perform checking for bit-shift overflows"
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default UBSAN
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depends on $(cc-option,-fsanitize=shift)
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help
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This option enables -fsanitize=shift which checks for bit-shift
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operations that overflow to the left or go switch to negative
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for signed types.
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config UBSAN_DIV_ZERO
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bool "Perform checking for integer divide-by-zero"
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depends on $(cc-option,-fsanitize=integer-divide-by-zero)
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help
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This option enables -fsanitize=integer-divide-by-zero which checks
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for integer division by zero. This is effectively redundant with the
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kernel's existing exception handling, though it can provide greater
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debugging information under CONFIG_UBSAN_REPORT_FULL.
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config UBSAN_UNREACHABLE
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bool "Perform checking for unreachable code"
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# objtool already handles unreachable checking and gets angry about
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# seeing UBSan instrumentation located in unreachable places.
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depends on !STACK_VALIDATION
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depends on $(cc-option,-fsanitize=unreachable)
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help
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This option enables -fsanitize=unreachable which checks for control
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flow reaching an expected-to-be-unreachable position.
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config UBSAN_OBJECT_SIZE
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bool "Perform checking for accesses beyond the end of objects"
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default UBSAN
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# gcc hugely expands stack usage with -fsanitize=object-size
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# https://lore.kernel.org/lkml/CAHk-=wjPasyJrDuwDnpHJS2TuQfExwe=px-SzLeN8GFMAQJPmQ@mail.gmail.com/
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depends on !CC_IS_GCC
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depends on $(cc-option,-fsanitize=object-size)
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help
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This option enables -fsanitize=object-size which checks for accesses
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beyond the end of objects where the optimizer can determine both the
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object being operated on and its size, usually seen with bad downcasts,
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or access to struct members from NULL pointers.
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config UBSAN_BOOL
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bool "Perform checking for non-boolean values used as boolean"
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default UBSAN
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depends on $(cc-option,-fsanitize=bool)
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help
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This option enables -fsanitize=bool which checks for boolean values being
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loaded that are neither 0 nor 1.
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config UBSAN_ENUM
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bool "Perform checking for out of bounds enum values"
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default UBSAN
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depends on $(cc-option,-fsanitize=enum)
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help
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This option enables -fsanitize=enum which checks for values being loaded
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into an enum that are outside the range of given values for the given enum.
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config UBSAN_ALIGNMENT
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bool "Perform checking for misaligned pointer usage"
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default !HAVE_EFFICIENT_UNALIGNED_ACCESS
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depends on !UBSAN_TRAP && !COMPILE_TEST
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depends on $(cc-option,-fsanitize=alignment)
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help
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This option enables the check of unaligned memory accesses.
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Enabling this option on architectures that support unaligned
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accesses may produce a lot of false positives.
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config UBSAN_SANITIZE_ALL
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bool "Enable instrumentation for the entire kernel"
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depends on ARCH_HAS_UBSAN_SANITIZE_ALL
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default y
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help
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This option activates instrumentation for the entire kernel.
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If you don't enable this option, you have to explicitly specify
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UBSAN_SANITIZE := y for the files/directories you want to check for UB.
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Enabling this option will get kernel image size increased
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significantly.
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config TEST_UBSAN
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tristate "Module for testing for undefined behavior detection"
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depends on m
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help
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This is a test module for UBSAN.
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It triggers various undefined behavior, and detect it.
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endif # if UBSAN
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