# 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 "Abort on Sanitizer warnings (smaller kernel but less verbose)" depends on !COMPILE_TEST 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. Also note that selecting Y will cause your kernel to Oops with an "illegal instruction" error with no further details when a UBSAN violation occurs. (Except on arm64 and x86, which will report which Sanitizer failed.) This may make it hard to determine whether an Oops was caused by UBSAN or to figure out the details of a UBSAN violation. It makes the kernel log output less useful for bug reports. config CC_HAS_UBSAN_BOUNDS_STRICT def_bool $(cc-option,-fsanitize=bounds-strict) help The -fsanitize=bounds-strict option is only available on GCC, but uses the more strict handling of arrays that includes knowledge of flexible arrays, which is comparable to Clang's regular -fsanitize=bounds. config CC_HAS_UBSAN_ARRAY_BOUNDS def_bool $(cc-option,-fsanitize=array-bounds) help Under Clang, the -fsanitize=bounds option is actually composed of two more specific options, -fsanitize=array-bounds and -fsanitize=local-bounds. However, -fsanitize=local-bounds can only be used when trap mode is enabled. (See also the help for CONFIG_LOCAL_BOUNDS.) Explicitly check for -fsanitize=array-bounds so that we can build up the options needed for UBSAN_BOUNDS with or without UBSAN_TRAP. config UBSAN_BOUNDS bool "Perform array index bounds checking" default UBSAN depends on CC_HAS_UBSAN_ARRAY_BOUNDS || CC_HAS_UBSAN_BOUNDS_STRICT 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_BOUNDS_STRICT def_bool UBSAN_BOUNDS && CC_HAS_UBSAN_BOUNDS_STRICT help GCC's bounds sanitizer. This option is used to select the correct options in Makefile.ubsan. config UBSAN_ARRAY_BOUNDS def_bool UBSAN_BOUNDS && CC_HAS_UBSAN_ARRAY_BOUNDS help Clang's array bounds sanitizer. This option is used to select the correct options in Makefile.ubsan. config UBSAN_LOCAL_BOUNDS def_bool UBSAN_ARRAY_BOUNDS && UBSAN_TRAP help This option enables Clang's -fsanitize=local-bounds which traps when an access 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. Since this option is trap-only, it depends on CONFIG_UBSAN_TRAP. 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) # https://github.com/ClangBuiltLinux/linux/issues/1657 # https://github.com/llvm/llvm-project/issues/56289 depends on !CC_IS_CLANG 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 !(OBJTOOL && (STACK_VALIDATION || UNWINDER_ORC || HAVE_UACCESS_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_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