From: Kees Cook <keescook@xxxxxxxxxxxx> Subject: ubsan: remove CONFIG_UBSAN_OBJECT_SIZE The object-size sanitizer is redundant to -Warray-bounds, and inappropriately performs its checks at run-time when all information needed for the evaluation is available at compile-time, making it quite difficult to use: https://bugzilla.kernel.org/show_bug.cgi?id=214861 With -Warray-bounds almost enabled globally, it doesn't make sense to keep this around. Link: https://lkml.kernel.org/r/20211203235346.110809-1-keescook@xxxxxxxxxxxx Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> Reviewed-by: Marco Elver <elver@xxxxxxxxxx> Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx> Cc: Michal Marek <michal.lkml@xxxxxxxxxxx> Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> Cc: Nathan Chancellor <nathan@xxxxxxxxxx> Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx> Cc: "Peter Zijlstra (Intel)" <peterz@xxxxxxxxxxxxx> Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> Cc: Arnd Bergmann <arnd@xxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- lib/Kconfig.ubsan | 13 ------------- lib/test_ubsan.c | 22 ---------------------- scripts/Makefile.ubsan | 1 - 3 files changed, 36 deletions(-) --- a/lib/Kconfig.ubsan~ubsan-remove-config_ubsan_object_size +++ a/lib/Kconfig.ubsan @@ -112,19 +112,6 @@ config UBSAN_UNREACHABLE This option enables -fsanitize=unreachable which checks for control flow reaching an expected-to-be-unreachable position. -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@xxxxxxxxxxxxxx/ - depends on !CC_IS_GCC - depends on $(cc-option,-fsanitize=object-size) - help - This option enables -fsanitize=object-size which checks for accesses - beyond the end of objects where the optimizer can determine both the - object being operated on and its size, usually seen with bad downcasts, - or access to struct members from NULL pointers. - config UBSAN_BOOL bool "Perform checking for non-boolean values used as boolean" default UBSAN --- a/lib/test_ubsan.c~ubsan-remove-config_ubsan_object_size +++ a/lib/test_ubsan.c @@ -79,15 +79,6 @@ static void test_ubsan_load_invalid_valu eval2 = eval; } -static void test_ubsan_null_ptr_deref(void) -{ - volatile int *ptr = NULL; - int val; - - UBSAN_TEST(CONFIG_UBSAN_OBJECT_SIZE); - val = *ptr; -} - static void test_ubsan_misaligned_access(void) { volatile char arr[5] __aligned(4) = {1, 2, 3, 4, 5}; @@ -98,29 +89,16 @@ static void test_ubsan_misaligned_access *ptr = val; } -static void test_ubsan_object_size_mismatch(void) -{ - /* "((aligned(8)))" helps this not into be misaligned for ptr-access. */ - volatile int val __aligned(8) = 4; - volatile long long *ptr, val2; - - UBSAN_TEST(CONFIG_UBSAN_OBJECT_SIZE); - ptr = (long long *)&val; - val2 = *ptr; -} - static const test_ubsan_fp test_ubsan_array[] = { test_ubsan_shift_out_of_bounds, test_ubsan_out_of_bounds, test_ubsan_load_invalid_value, test_ubsan_misaligned_access, - test_ubsan_object_size_mismatch, }; /* Excluded because they Oops the module. */ static const test_ubsan_fp skip_ubsan_array[] = { test_ubsan_divrem_overflow, - test_ubsan_null_ptr_deref, }; static int __init test_ubsan_init(void) --- a/scripts/Makefile.ubsan~ubsan-remove-config_ubsan_object_size +++ a/scripts/Makefile.ubsan @@ -8,7 +8,6 @@ ubsan-cflags-$(CONFIG_UBSAN_LOCAL_BOUNDS ubsan-cflags-$(CONFIG_UBSAN_SHIFT) += -fsanitize=shift ubsan-cflags-$(CONFIG_UBSAN_DIV_ZERO) += -fsanitize=integer-divide-by-zero ubsan-cflags-$(CONFIG_UBSAN_UNREACHABLE) += -fsanitize=unreachable -ubsan-cflags-$(CONFIG_UBSAN_OBJECT_SIZE) += -fsanitize=object-size ubsan-cflags-$(CONFIG_UBSAN_BOOL) += -fsanitize=bool ubsan-cflags-$(CONFIG_UBSAN_ENUM) += -fsanitize=enum ubsan-cflags-$(CONFIG_UBSAN_TRAP) += -fsanitize-undefined-trap-on-error _
