When the kernel is compiled with Clang, -fsanitize=bounds expands to
-fsanitize=array-bounds and -fsanitize=local-bounds.
Enabling -fsanitize=local-bounds with Clang has the unfortunate
side-effect of inserting traps; this goes back to its original intent,
which was as a hardening and not a debugging feature [1]. The same
feature made its way into -fsanitize=bounds, but the traps remained. For
that reason, -fsanitize=bounds was split into 'array-bounds' and
'local-bounds' [2].
Since 'local-bounds' doesn't behave like a normal sanitizer, enable it
with Clang only if trapping behaviour was requested by
CONFIG_UBSAN_TRAP=y.
Add the UBSAN_BOUNDS_LOCAL config to Kconfig.ubsan to enable the
'local-bounds' option by default when UBSAN_TRAP is enabled.
[1] http://lists.llvm.org/pipermail/llvm-dev/2012-May/049972.html
[2] http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-
20131021/091536.html
Suggested-by: Marco Elver <elver@google.com>
Signed-off-by: George Popescu <georgepope@android.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: David Brazdil <dbrazdil@google.com>
Reviewed-by: 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: Kees Cook <keescook@chromium.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: https://lkml.kernel.org/r/20200922074330.2549523-1-georgepope@google.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
to the {str,mem}*cpy() family of functions (that is addressed
by CONFIG_FORTIFY_SOURCE).
+config UBSAN_LOCAL_BOUNDS
+ bool "Perform array local bounds checking"
+ depends on UBSAN_TRAP
+ depends on CC_IS_CLANG
+ depends on !UBSAN_KCOV_BROKEN
+ help
+ This option enables -fsanitize=local-bounds which traps when an
+ exception/error is detected. Therefore, it should be enabled only
+ if trapping is expected.
+ 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_MISC
bool "Enable all other Undefined Behavior sanity checks"
default UBSAN
endif
ifdef CONFIG_UBSAN_BOUNDS
- CFLAGS_UBSAN += $(call cc-option, -fsanitize=bounds)
+ ifdef CONFIG_CC_IS_CLANG
+ CFLAGS_UBSAN += -fsanitize=array-bounds
+ else
+ CFLAGS_UBSAN += $(call cc-option, -fsanitize=bounds)
+ endif
+endif
+
+ifdef CONFIG_UBSAN_LOCAL_BOUNDS
+ CFLAGS_UBSAN += -fsanitize=local-bounds
endif
ifdef CONFIG_UBSAN_MISC