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linux/lib/Kconfig.ubsan
Kees Cook c637693b20 ubsan: remove UBSAN_MISC in favor of individual options 
Make each UBSAN option individually selectable and remove UBSAN_MISC which
no longer has any purpose.  Add help text for each Kconfig, and include a
reference to the Clang sanitizer documentation.  Disable unsigned overflow
by default (not available with GCC and makes x86 unbootable with Clang).
Disable unreachable when objtool is in use (redundant and confuses things:
instrumentation appears at unreachable locations).

Link: https://lkml.kernel.org/r/20201203004437.389959-7-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: George Popescu <georgepope@android.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Marco Elver <elver@google.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Nathan Chancellor <natechancellor@gmail.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Peter Oberparleiter <oberpar@linux.ibm.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-12-15 22:46:19 -08:00

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# SPDX-License-Identifier: GPL-2.0-only
config ARCH_HAS_UBSAN_SANITIZE_ALL
bool
menuconfig UBSAN
bool "Undefined behaviour sanity checker"
help
This option enables the Undefined Behaviour sanity checker.
Compile-time instrumentation is used to detect various undefined
behaviours at runtime. For more details, see:
Documentation/dev-tools/ubsan.rst
if UBSAN
config UBSAN_TRAP
bool "On Sanitizer warnings, abort the running kernel code"
depends on !COMPILE_TEST
depends on $(cc-option, -fsanitize-undefined-trap-on-error)
help
Building kernels with Sanitizer features enabled tends to grow
the kernel size by around 5%, due to adding all the debugging
text on failure paths. To avoid this, Sanitizer instrumentation
can just issue a trap. This reduces the kernel size overhead but
turns all warnings (including potentially harmless conditions)
into full exceptions that abort the running kernel code
(regardless of context, locks held, etc), which may destabilize
the system. For some system builders this is an acceptable
trade-off.
config UBSAN_KCOV_BROKEN
def_bool KCOV && CC_HAS_SANCOV_TRACE_PC
depends on CC_IS_CLANG
depends on !$(cc-option,-Werror=unused-command-line-argument -fsanitize=bounds -fsanitize-coverage=trace-pc)
help
Some versions of clang support either UBSAN or KCOV but not the
combination of the two.
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.
Note that this does not protect array overflows via bad calls
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 !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 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
out-of-bounds.
config UBSAN_SHIFT
bool "Perform checking for bit-shift overflows"
default UBSAN
depends on $(cc-option,-fsanitize=shift)
help
This option enables -fsanitize=shift which checks for bit-shift
operations that overflow to the left or go switch to negative
for signed types.
config UBSAN_DIV_ZERO
bool "Perform checking for integer divide-by-zero"
depends on $(cc-option,-fsanitize=integer-divide-by-zero)
help
This option enables -fsanitize=integer-divide-by-zero which checks
for integer division by zero. This is effectively redundant with the
kernel's existing exception handling, though it can provide greater
debugging information under CONFIG_UBSAN_REPORT_FULL.
config UBSAN_UNREACHABLE
bool "Perform checking for unreachable code"
# objtool already handles unreachable checking and gets angry about
# seeing UBSan instrumentation located in unreachable places.
depends on !STACK_VALIDATION
depends on $(cc-option,-fsanitize=unreachable)
help
This option enables -fsanitize=unreachable which checks for control
flow reaching an expected-to-be-unreachable position.
config UBSAN_SIGNED_OVERFLOW
bool "Perform checking for signed arithmetic overflow"
default UBSAN
depends on $(cc-option,-fsanitize=signed-integer-overflow)
help
This option enables -fsanitize=signed-integer-overflow which checks
for overflow of any arithmetic operations with signed integers.
config UBSAN_UNSIGNED_OVERFLOW
bool "Perform checking for unsigned arithmetic overflow"
depends on $(cc-option,-fsanitize=unsigned-integer-overflow)
help
This option enables -fsanitize=unsigned-integer-overflow which checks
for overflow of any arithmetic operations with unsigned integers. This
currently causes x86 to fail to boot.
config UBSAN_OBJECT_SIZE
bool "Perform checking for accesses beyond the end of objects"
default UBSAN
# gcc hugely expands stack usage with -fsanitize=object-size
# https://lore.kernel.org/lkml/CAHk-=wjPasyJrDuwDnpHJS2TuQfExwe=px-SzLeN8GFMAQJPmQ@mail.gmail.com/
depends on !CC_IS_GCC
depends on $(cc-option,-fsanitize=object-size)
help
This option enables -fsanitize=object-size which checks for accesses
beyond the end of objects where the optimizer can determine both the
object being operated on and its size, usually seen with bad downcasts,
or access to struct members from NULL pointers.
config UBSAN_BOOL
bool "Perform checking for non-boolean values used as boolean"
default UBSAN
depends on $(cc-option,-fsanitize=bool)
help
This option enables -fsanitize=bool which checks for boolean values being
loaded that are neither 0 nor 1.
config UBSAN_ENUM
bool "Perform checking for out of bounds enum values"
default UBSAN
depends on $(cc-option,-fsanitize=enum)
help
This option enables -fsanitize=enum which checks for values being loaded
into an enum that are outside the range of given values for the given enum.
config UBSAN_ALIGNMENT
bool "Perform checking for misaligned pointer usage"
default !HAVE_EFFICIENT_UNALIGNED_ACCESS
depends on !UBSAN_TRAP && !COMPILE_TEST
depends on $(cc-option,-fsanitize=alignment)
help
This option enables the check of unaligned memory accesses.
Enabling this option on architectures that support unaligned
accesses may produce a lot of false positives.
config UBSAN_SANITIZE_ALL
bool "Enable instrumentation for the entire kernel"
depends on ARCH_HAS_UBSAN_SANITIZE_ALL
default y
help
This option activates instrumentation for the entire kernel.
If you don't enable this option, you have to explicitly specify
UBSAN_SANITIZE := y for the files/directories you want to check for UB.
Enabling this option will get kernel image size increased
significantly.
config TEST_UBSAN
tristate "Module for testing for undefined behavior detection"
depends on m
help
This is a test module for UBSAN.
It triggers various undefined behavior, and detect it.
endif # if UBSAN
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