From 6aaa31aeb9cf260e1b7155cc11ec864f052db5ec Mon Sep 17 00:00:00 2001 From: Andrey Ryabinin Date: Thu, 25 Feb 2021 17:22:42 -0800 Subject: [PATCH] ubsan: remove overflow checks Since GCC 8.0 -fsanitize=signed-integer-overflow doesn't work with -fwrapv. -fwrapv makes signed overflows defines and GCC essentially disables ubsan checks. On GCC < 8.0 -fwrapv doesn't have influence on -fsanitize=signed-integer-overflow setting, so it kinda works but generates false-positves and violates uaccess rules: lib/iov_iter.o: warning: objtool: iovec_from_user()+0x22d: call to __ubsan_handle_add_overflow() with UACCESS enabled Disable signed overflow checks to avoid these problems. Remove unsigned overflow checks as well. Unsigned overflow appeared as side effect of commit cdf8a76fda4a ("ubsan: move cc-option tests into Kconfig"), but it never worked (kernel doesn't boot). And unsigned overflows are allowed by C standard, so it just pointless. Link: https://lkml.kernel.org/r/20210209232348.20510-1-ryabinin.a.a@gmail.com Signed-off-by: Andrey Ryabinin Acked-by: Peter Zijlstra (Intel) Cc: Josh Poimboeuf Cc: Randy Dunlap Cc: Stephen Rothwell Cc: Dmitry Vyukov Cc: Kees Cook Cc: Alexander Viro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- lib/Kconfig.ubsan | 17 ----------- lib/test_ubsan.c | 49 ------------------------------ lib/ubsan.c | 68 ------------------------------------------ scripts/Makefile.ubsan | 2 -- 4 files changed, 136 deletions(-) diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan index 3a0b1c930733..e5372a13511d 100644 --- a/lib/Kconfig.ubsan +++ b/lib/Kconfig.ubsan @@ -112,23 +112,6 @@ config UBSAN_UNREACHABLE 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) - depends on !X86_32 # avoid excessive stack usage on x86-32/clang - 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 diff --git a/lib/test_ubsan.c b/lib/test_ubsan.c index 5e5d9355ef49..7e7bbd0f3fd2 100644 --- a/lib/test_ubsan.c +++ b/lib/test_ubsan.c @@ -11,51 +11,6 @@ typedef void(*test_ubsan_fp)(void); #config, IS_ENABLED(config) ? "y" : "n"); \ } while (0) -static void test_ubsan_add_overflow(void) -{ - volatile int val = INT_MAX; - volatile unsigned int uval = UINT_MAX; - - UBSAN_TEST(CONFIG_UBSAN_SIGNED_OVERFLOW); - val += 2; - - UBSAN_TEST(CONFIG_UBSAN_UNSIGNED_OVERFLOW); - uval += 2; -} - -static void test_ubsan_sub_overflow(void) -{ - volatile int val = INT_MIN; - volatile unsigned int uval = 0; - volatile int val2 = 2; - - UBSAN_TEST(CONFIG_UBSAN_SIGNED_OVERFLOW); - val -= val2; - - UBSAN_TEST(CONFIG_UBSAN_UNSIGNED_OVERFLOW); - uval -= val2; -} - -static void test_ubsan_mul_overflow(void) -{ - volatile int val = INT_MAX / 2; - volatile unsigned int uval = UINT_MAX / 2; - - UBSAN_TEST(CONFIG_UBSAN_SIGNED_OVERFLOW); - val *= 3; - - UBSAN_TEST(CONFIG_UBSAN_UNSIGNED_OVERFLOW); - uval *= 3; -} - -static void test_ubsan_negate_overflow(void) -{ - volatile int val = INT_MIN; - - UBSAN_TEST(CONFIG_UBSAN_SIGNED_OVERFLOW); - val = -val; -} - static void test_ubsan_divrem_overflow(void) { volatile int val = 16; @@ -155,10 +110,6 @@ static void test_ubsan_object_size_mismatch(void) } static const test_ubsan_fp test_ubsan_array[] = { - test_ubsan_add_overflow, - test_ubsan_sub_overflow, - test_ubsan_mul_overflow, - test_ubsan_negate_overflow, test_ubsan_shift_out_of_bounds, test_ubsan_out_of_bounds, test_ubsan_load_invalid_value, diff --git a/lib/ubsan.c b/lib/ubsan.c index bec38c64d6a6..26229973049d 100644 --- a/lib/ubsan.c +++ b/lib/ubsan.c @@ -163,74 +163,6 @@ static void ubsan_epilogue(void) } } -static void handle_overflow(struct overflow_data *data, void *lhs, - void *rhs, char op) -{ - - struct type_descriptor *type = data->type; - char lhs_val_str[VALUE_LENGTH]; - char rhs_val_str[VALUE_LENGTH]; - - if (suppress_report(&data->location)) - return; - - ubsan_prologue(&data->location, type_is_signed(type) ? - "signed-integer-overflow" : - "unsigned-integer-overflow"); - - val_to_string(lhs_val_str, sizeof(lhs_val_str), type, lhs); - val_to_string(rhs_val_str, sizeof(rhs_val_str), type, rhs); - pr_err("%s %c %s cannot be represented in type %s\n", - lhs_val_str, - op, - rhs_val_str, - type->type_name); - - ubsan_epilogue(); -} - -void __ubsan_handle_add_overflow(void *data, - void *lhs, void *rhs) -{ - - handle_overflow(data, lhs, rhs, '+'); -} -EXPORT_SYMBOL(__ubsan_handle_add_overflow); - -void __ubsan_handle_sub_overflow(void *data, - void *lhs, void *rhs) -{ - handle_overflow(data, lhs, rhs, '-'); -} -EXPORT_SYMBOL(__ubsan_handle_sub_overflow); - -void __ubsan_handle_mul_overflow(void *data, - void *lhs, void *rhs) -{ - handle_overflow(data, lhs, rhs, '*'); -} -EXPORT_SYMBOL(__ubsan_handle_mul_overflow); - -void __ubsan_handle_negate_overflow(void *_data, void *old_val) -{ - struct overflow_data *data = _data; - char old_val_str[VALUE_LENGTH]; - - if (suppress_report(&data->location)) - return; - - ubsan_prologue(&data->location, "negation-overflow"); - - val_to_string(old_val_str, sizeof(old_val_str), data->type, old_val); - - pr_err("negation of %s cannot be represented in type %s:\n", - old_val_str, data->type->type_name); - - ubsan_epilogue(); -} -EXPORT_SYMBOL(__ubsan_handle_negate_overflow); - - void __ubsan_handle_divrem_overflow(void *_data, void *lhs, void *rhs) { struct overflow_data *data = _data; diff --git a/scripts/Makefile.ubsan b/scripts/Makefile.ubsan index 0e53a93e8f15..9e2092fd5206 100644 --- a/scripts/Makefile.ubsan +++ b/scripts/Makefile.ubsan @@ -8,8 +8,6 @@ ubsan-cflags-$(CONFIG_UBSAN_LOCAL_BOUNDS) += -fsanitize=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_SIGNED_OVERFLOW) += -fsanitize=signed-integer-overflow -ubsan-cflags-$(CONFIG_UBSAN_UNSIGNED_OVERFLOW) += -fsanitize=unsigned-integer-overflow ubsan-cflags-$(CONFIG_UBSAN_OBJECT_SIZE) += -fsanitize=object-size ubsan-cflags-$(CONFIG_UBSAN_BOOL) += -fsanitize=bool ubsan-cflags-$(CONFIG_UBSAN_ENUM) += -fsanitize=enum