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ce6616724f
Make it clearer in the one-line description and the verbose description text that CONFIG_UBSAN_TRAP as currently implemented involves a tradeoff of much less helpful oops messages in exchange for a smaller kernel image. (With the additional effect of turning UBSAN warnings into crashes, which may or may not be desired.) Signed-off-by: Jann Horn <jannh@google.com> Link: https://lore.kernel.org/r/20230705215128.486054-1-jannh@google.com Signed-off-by: Kees Cook <keescook@chromium.org>
164 lines
6.2 KiB
Plaintext
164 lines
6.2 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 "Abort on Sanitizer warnings (smaller kernel but less verbose)"
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depends on !COMPILE_TEST
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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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Also note that selecting Y will cause your kernel to Oops
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with an "illegal instruction" error with no further details
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when a UBSAN violation occurs. (Except on arm64, which will
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report which Sanitizer failed.) This may make it hard to
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determine whether an Oops was caused by UBSAN or to figure
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out the details of a UBSAN violation. It makes the kernel log
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output less useful for bug reports.
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config CC_HAS_UBSAN_BOUNDS_STRICT
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def_bool $(cc-option,-fsanitize=bounds-strict)
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help
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The -fsanitize=bounds-strict option is only available on GCC,
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but uses the more strict handling of arrays that includes knowledge
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of flexible arrays, which is comparable to Clang's regular
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-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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help
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Under Clang, the -fsanitize=bounds option is actually composed
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of two more specific options, -fsanitize=array-bounds and
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-fsanitize=local-bounds. However, -fsanitize=local-bounds can
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only be used when trap mode is enabled. (See also the help for
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CONFIG_LOCAL_BOUNDS.) Explicitly check for -fsanitize=array-bounds
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so that we can build up the options needed for UBSAN_BOUNDS
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with or without UBSAN_TRAP.
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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 CC_HAS_UBSAN_ARRAY_BOUNDS || CC_HAS_UBSAN_BOUNDS_STRICT
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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_BOUNDS_STRICT
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def_bool UBSAN_BOUNDS && CC_HAS_UBSAN_BOUNDS_STRICT
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help
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GCC's bounds sanitizer. This option is used to select the
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correct options in Makefile.ubsan.
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config UBSAN_ARRAY_BOUNDS
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def_bool UBSAN_BOUNDS && CC_HAS_UBSAN_ARRAY_BOUNDS
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help
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Clang's array bounds sanitizer. This option is used to select
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the correct options in Makefile.ubsan.
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config UBSAN_LOCAL_BOUNDS
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def_bool UBSAN_ARRAY_BOUNDS && UBSAN_TRAP
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help
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This option enables Clang's -fsanitize=local-bounds which traps
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when an access through a pointer that is derived from an object
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of a statically-known size, where an added offset (which may not
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be known statically) is out-of-bounds. Since this option is
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trap-only, it depends on CONFIG_UBSAN_TRAP.
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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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# https://github.com/ClangBuiltLinux/linux/issues/1657
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# https://github.com/llvm/llvm-project/issues/56289
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depends on !CC_IS_CLANG
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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 !(OBJTOOL && (STACK_VALIDATION || UNWINDER_ORC || HAVE_UACCESS_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_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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