* [PATCH v11.5] overflow: Introduce overflows_type() and __castable_to_type() [not found] <202209251032.71251A8@keescook> @ 2022-09-26 0:37 ` Kees Cook 2022-09-26 9:53 ` Gwan-gyeong Mun 2022-09-26 15:57 ` Gwan-gyeong Mun 0 siblings, 2 replies; 4+ messages in thread From: Kees Cook @ 2022-09-26 0:37 UTC (permalink / raw) To: Gwan-gyeong Mun Cc: Kees Cook, Luc Van Oostenryck, Nathan Chancellor, Nick Desaulniers, Tom Rix, Daniel Latypov, Vitor Massaru Iha, Gustavo A. R. Silva, linux-hardening, llvm, intel-gfx, linux-kernel, dri-devel, mchehab, chris, matthew.auld, thomas.hellstrom, jani.nikula, nirmoy.das, airlied, daniel, andi.shyti, andrzej.hajda, mauro.chehab, linux, linux-sparse Add overflows_type() to test if a variable or constant value would overflow another variable or type. This can be used as a constant expression for static_assert() (which requires a constant expression[1][2]) when used on constant values. This must be constructed manually, since __builtin_add_overflow() does not produce a constant expression[3]. Additionally adds __castable_to_type(), similar to __same_type(), for checking if a constant value will fit in a given type (i.e. it could be cast to the type without overflow). Add unit tests for overflows_type(), __same_type(), and __castable_to_type() to the existing KUnit "overflow" test. [1] https://en.cppreference.com/w/c/language/_Static_assert [2] C11 standard (ISO/IEC 9899:2011): 6.7.10 Static assertions [3] https://gcc.gnu.org/onlinedocs/gcc/Integer-Overflow-Builtins.html 6.56 Built-in Functions to Perform Arithmetic with Overflow Checking Built-in Function: bool __builtin_add_overflow (type1 a, type2 b, type3 *res) Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com> Cc: Nathan Chancellor <nathan@kernel.org> Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Tom Rix <trix@redhat.com> Cc: Daniel Latypov <dlatypov@google.com> Cc: Vitor Massaru Iha <vitor@massaru.org> Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org> Cc: linux-hardening@vger.kernel.org Cc: llvm@lists.linux.dev Co-developed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com> Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com> Signed-off-by: Kees Cook <keescook@chromium.org> --- include/linux/compiler.h | 1 + include/linux/overflow.h | 48 +++++ lib/overflow_kunit.c | 393 ++++++++++++++++++++++++++++++++++++++- 3 files changed, 441 insertions(+), 1 deletion(-) diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 7713d7bcdaea..c631107e93b1 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -244,6 +244,7 @@ static inline void *offset_to_ptr(const int *off) * bool and also pointer types. */ #define is_signed_type(type) (((type)(-1)) < (__force type)1) +#define is_unsigned_type(type) (!is_signed_type(type)) /* * This is needed in functions which generate the stack canary, see diff --git a/include/linux/overflow.h b/include/linux/overflow.h index 19dfdd74835e..c8cbeae5f4f8 100644 --- a/include/linux/overflow.h +++ b/include/linux/overflow.h @@ -127,6 +127,54 @@ static inline bool __must_check __must_check_overflow(bool overflow) (*_d >> _to_shift) != _a); \ })) +#define __overflows_type_constexpr(x, T) ( \ + is_unsigned_type(typeof(x)) ? \ + (x) > type_max(typeof(T)) ? 1 : 0 \ + : is_unsigned_type(typeof(T)) ? \ + (x) < 0 || (x) > type_max(typeof(T)) ? 1 : 0 \ + : (x) < type_min(typeof(T)) || \ + (x) > type_max(typeof(T)) ? 1 : 0 ) + +#define __overflows_type(x, T) ({ \ + typeof(T) v = 0; \ + check_add_overflow((x), v, &v); \ +}) + +/** + * overflows_type - helper for checking the overflows between value, variables, + * or data type + * + * @n: source constant value or variable to be checked + * @T: destination variable or data type proposed to store @x + * + * Compares the @x expression for whether or not it can safely fit in + * the storage of the type in @T. @x and @T can have different types. + * If @x is a conxtant expression, this will also resolve to a constant + * expression. + * + * Returns: true if overflow can occur, false otherwise. + */ +#define overflows_type(n, T) \ + __builtin_choose_expr(__is_constexpr(n), \ + __overflows_type_constexpr(n, T), \ + __overflows_type(n, T)) + +/** + * __castable_to_type - like __same_type(), but also allows for casted literals + * + * @n: variable or constant value + * @T: data type or variable + * + * Unlike the __same_type() macro, this allows a constant value as the + * first argument. If this value would not overflow into an assignment + * of the second argument's type, it returns true. Otherwise, this falls + * back to __same_type(). + */ +#define __castable_to_type(n, T) \ + __builtin_choose_expr(__is_constexpr(n), \ + !__overflows_type_constexpr(n, T), \ + __same_type(n, T)) + /** * size_mul() - Calculate size_t multiplication with saturation at SIZE_MAX * diff --git a/lib/overflow_kunit.c b/lib/overflow_kunit.c index f385ca652b74..9331d6ce914e 100644 --- a/lib/overflow_kunit.c +++ b/lib/overflow_kunit.c @@ -16,6 +16,9 @@ #include <linux/types.h> #include <linux/vmalloc.h> +/* We're expecting to do a lot of "always true" or "always false" tests. */ +#pragma clang diagnostic ignored "-Wtautological-constant-out-of-range-compare" + #define DEFINE_TEST_ARRAY_TYPED(t1, t2, t) \ static const struct test_ ## t1 ## _ ## t2 ## __ ## t { \ t1 a; \ @@ -246,7 +249,7 @@ DEFINE_TEST_ARRAY(s64) = { #define DEFINE_TEST_FUNC_TYPED(n, t, fmt) \ static void do_test_ ## n(struct kunit *test, const struct test_ ## n *p) \ -{ \ +{ \ check_one_op(t, fmt, add, "+", p->a, p->b, p->sum, p->s_of); \ check_one_op(t, fmt, add, "+", p->b, p->a, p->sum, p->s_of); \ check_one_op(t, fmt, sub, "-", p->a, p->b, p->diff, p->d_of); \ @@ -708,6 +711,391 @@ static void overflow_size_helpers_test(struct kunit *test) #undef check_one_size_helper } +static void overflows_type_test(struct kunit *test) +{ + int count = 0; + unsigned int var; + +#define __TEST_OVERFLOWS_TYPE(func, arg1, arg2, of) do { \ + bool __of = func(arg1, arg2); \ + KUNIT_EXPECT_EQ_MSG(test, __of, of, \ + "expected " #func "(" #arg1 ", " #arg2 " to%s overflow\n",\ + of ? "" : " not"); \ + count++; \ +} while (0) + +/* Args are: first type, second type, value, overflow expected */ +#define TEST_OVERFLOWS_TYPE(__t1, __t2, v, of) do { \ + __t1 t1 = (v); \ + __t2 t2; \ + __TEST_OVERFLOWS_TYPE(__overflows_type, t1, t2, of); \ + __TEST_OVERFLOWS_TYPE(__overflows_type, t1, __t2, of); \ + __TEST_OVERFLOWS_TYPE(__overflows_type_constexpr, t1, t2, of); \ + __TEST_OVERFLOWS_TYPE(__overflows_type_constexpr, t1, __t2, of);\ +} while (0) + + TEST_OVERFLOWS_TYPE(u8, u8, U8_MAX, false); + TEST_OVERFLOWS_TYPE(u8, u16, U8_MAX, false); + TEST_OVERFLOWS_TYPE(u8, s8, U8_MAX, true); + TEST_OVERFLOWS_TYPE(u8, s8, S8_MAX, false); + TEST_OVERFLOWS_TYPE(u8, s8, (u8)S8_MAX + 1, true); + TEST_OVERFLOWS_TYPE(u8, s16, U8_MAX, false); + TEST_OVERFLOWS_TYPE(s8, u8, S8_MAX, false); + TEST_OVERFLOWS_TYPE(s8, u8, -1, true); + TEST_OVERFLOWS_TYPE(s8, u8, S8_MIN, true); + TEST_OVERFLOWS_TYPE(s8, u16, S8_MAX, false); + TEST_OVERFLOWS_TYPE(s8, u16, -1, true); + TEST_OVERFLOWS_TYPE(s8, u16, S8_MIN, true); + TEST_OVERFLOWS_TYPE(s8, u32, S8_MAX, false); + TEST_OVERFLOWS_TYPE(s8, u32, -1, true); + TEST_OVERFLOWS_TYPE(s8, u32, S8_MIN, true); +#if BITS_PER_LONG == 64 + TEST_OVERFLOWS_TYPE(s8, u64, S8_MAX, false); + TEST_OVERFLOWS_TYPE(s8, u64, -1, true); + TEST_OVERFLOWS_TYPE(s8, u64, S8_MIN, true); +#endif + TEST_OVERFLOWS_TYPE(s8, s8, S8_MAX, false); + TEST_OVERFLOWS_TYPE(s8, s8, S8_MIN, false); + TEST_OVERFLOWS_TYPE(s8, s16, S8_MAX, false); + TEST_OVERFLOWS_TYPE(s8, s16, S8_MIN, false); + TEST_OVERFLOWS_TYPE(u16, u8, U8_MAX, false); + TEST_OVERFLOWS_TYPE(u16, u8, (u16)U8_MAX + 1, true); + TEST_OVERFLOWS_TYPE(u16, u8, U16_MAX, true); + TEST_OVERFLOWS_TYPE(u16, s8, S8_MAX, false); + TEST_OVERFLOWS_TYPE(u16, s8, (u16)S8_MAX + 1, true); + TEST_OVERFLOWS_TYPE(u16, s8, U16_MAX, true); + TEST_OVERFLOWS_TYPE(u16, s16, S16_MAX, false); + TEST_OVERFLOWS_TYPE(u16, s16, (u16)S16_MAX + 1, true); + TEST_OVERFLOWS_TYPE(u16, s16, U16_MAX, true); + TEST_OVERFLOWS_TYPE(u16, u32, U16_MAX, false); + TEST_OVERFLOWS_TYPE(u16, s32, U16_MAX, false); + TEST_OVERFLOWS_TYPE(s16, u8, U8_MAX, false); + TEST_OVERFLOWS_TYPE(s16, u8, (s16)U8_MAX + 1, true); + TEST_OVERFLOWS_TYPE(s16, u8, -1, true); + TEST_OVERFLOWS_TYPE(s16, u8, S16_MIN, true); + TEST_OVERFLOWS_TYPE(s16, u16, S16_MAX, false); + TEST_OVERFLOWS_TYPE(s16, u16, -1, true); + TEST_OVERFLOWS_TYPE(s16, u16, S16_MIN, true); + TEST_OVERFLOWS_TYPE(s16, u32, S16_MAX, false); + TEST_OVERFLOWS_TYPE(s16, u32, -1, true); + TEST_OVERFLOWS_TYPE(s16, u32, S16_MIN, true); +#if BITS_PER_LONG == 64 + TEST_OVERFLOWS_TYPE(s16, u64, S16_MAX, false); + TEST_OVERFLOWS_TYPE(s16, u64, -1, true); + TEST_OVERFLOWS_TYPE(s16, u64, S16_MIN, true); +#endif + TEST_OVERFLOWS_TYPE(s16, s8, S8_MAX, false); + TEST_OVERFLOWS_TYPE(s16, s8, S8_MIN, false); + TEST_OVERFLOWS_TYPE(s16, s8, (s16)S8_MAX + 1, true); + TEST_OVERFLOWS_TYPE(s16, s8, (s16)S8_MIN - 1, true); + TEST_OVERFLOWS_TYPE(s16, s8, S16_MAX, true); + TEST_OVERFLOWS_TYPE(s16, s8, S16_MIN, true); + TEST_OVERFLOWS_TYPE(s16, s16, S16_MAX, false); + TEST_OVERFLOWS_TYPE(s16, s16, S16_MIN, false); + TEST_OVERFLOWS_TYPE(s16, s32, S16_MAX, false); + TEST_OVERFLOWS_TYPE(s16, s32, S16_MIN, false); + TEST_OVERFLOWS_TYPE(u32, u8, U8_MAX, false); + TEST_OVERFLOWS_TYPE(u32, u8, (u32)U8_MAX + 1, true); + TEST_OVERFLOWS_TYPE(u32, u8, U32_MAX, true); + TEST_OVERFLOWS_TYPE(u32, s8, S8_MAX, false); + TEST_OVERFLOWS_TYPE(u32, s8, (u32)S8_MAX + 1, true); + TEST_OVERFLOWS_TYPE(u32, s8, U32_MAX, true); + TEST_OVERFLOWS_TYPE(u32, u16, U16_MAX, false); + TEST_OVERFLOWS_TYPE(u32, u16, U16_MAX + 1, true); + TEST_OVERFLOWS_TYPE(u32, u16, U32_MAX, true); + TEST_OVERFLOWS_TYPE(u32, s16, S16_MAX, false); + TEST_OVERFLOWS_TYPE(u32, s16, (u32)S16_MAX + 1, true); + TEST_OVERFLOWS_TYPE(u32, s16, U32_MAX, true); + TEST_OVERFLOWS_TYPE(u32, u32, U32_MAX, false); + TEST_OVERFLOWS_TYPE(u32, s32, S32_MAX, false); + TEST_OVERFLOWS_TYPE(u32, s32, U32_MAX, true); + TEST_OVERFLOWS_TYPE(u32, s32, (u32)S32_MAX + 1, true); +#if BITS_PER_LONG == 64 + TEST_OVERFLOWS_TYPE(u32, u64, U32_MAX, false); + TEST_OVERFLOWS_TYPE(u32, s64, U32_MAX, false); +#endif + TEST_OVERFLOWS_TYPE(s32, u8, U8_MAX, false); + TEST_OVERFLOWS_TYPE(s32, u8, (s32)U8_MAX + 1, true); + TEST_OVERFLOWS_TYPE(s32, u16, S32_MAX, true); + TEST_OVERFLOWS_TYPE(s32, u8, -1, true); + TEST_OVERFLOWS_TYPE(s32, u8, S32_MIN, true); + TEST_OVERFLOWS_TYPE(s32, u16, U16_MAX, false); + TEST_OVERFLOWS_TYPE(s32, u16, (s32)U16_MAX + 1, true); + TEST_OVERFLOWS_TYPE(s32, u16, S32_MAX, true); + TEST_OVERFLOWS_TYPE(s32, u16, -1, true); + TEST_OVERFLOWS_TYPE(s32, u16, S32_MIN, true); + TEST_OVERFLOWS_TYPE(s32, u32, S32_MAX, false); + TEST_OVERFLOWS_TYPE(s32, u32, -1, true); + TEST_OVERFLOWS_TYPE(s32, u32, S32_MIN, true); +#if BITS_PER_LONG == 64 + TEST_OVERFLOWS_TYPE(s32, u64, S32_MAX, false); + TEST_OVERFLOWS_TYPE(s32, u64, -1, true); + TEST_OVERFLOWS_TYPE(s32, u64, S32_MIN, true); +#endif + TEST_OVERFLOWS_TYPE(s32, s8, S8_MAX, false); + TEST_OVERFLOWS_TYPE(s32, s8, S8_MIN, false); + TEST_OVERFLOWS_TYPE(s32, s8, (s32)S8_MAX + 1, true); + TEST_OVERFLOWS_TYPE(s32, s8, (s32)S8_MIN - 1, true); + TEST_OVERFLOWS_TYPE(s32, s8, S32_MAX, true); + TEST_OVERFLOWS_TYPE(s32, s8, S32_MIN, true); + TEST_OVERFLOWS_TYPE(s32, s16, S16_MAX, false); + TEST_OVERFLOWS_TYPE(s32, s16, S16_MIN, false); + TEST_OVERFLOWS_TYPE(s32, s16, (s32)S16_MAX + 1, true); + TEST_OVERFLOWS_TYPE(s32, s16, (s32)S16_MIN - 1, true); + TEST_OVERFLOWS_TYPE(s32, s16, S32_MAX, true); + TEST_OVERFLOWS_TYPE(s32, s16, S32_MIN, true); + TEST_OVERFLOWS_TYPE(s32, s32, S32_MAX, false); + TEST_OVERFLOWS_TYPE(s32, s32, S32_MIN, false); +#if BITS_PER_LONG == 64 + TEST_OVERFLOWS_TYPE(s32, s64, S32_MAX, false); + TEST_OVERFLOWS_TYPE(s32, s64, S32_MIN, false); + TEST_OVERFLOWS_TYPE(u64, u8, U64_MAX, true); + TEST_OVERFLOWS_TYPE(u64, u8, U8_MAX, false); + TEST_OVERFLOWS_TYPE(u64, u8, (u64)U8_MAX + 1, true); + TEST_OVERFLOWS_TYPE(u64, u16, U64_MAX, true); + TEST_OVERFLOWS_TYPE(u64, u16, U16_MAX, false); + TEST_OVERFLOWS_TYPE(u64, u16, (u64)U16_MAX + 1, true); + TEST_OVERFLOWS_TYPE(u64, u32, U64_MAX, true); + TEST_OVERFLOWS_TYPE(u64, u32, U32_MAX, false); + TEST_OVERFLOWS_TYPE(u64, u32, (u64)U32_MAX + 1, true); + TEST_OVERFLOWS_TYPE(u64, u64, U64_MAX, false); + TEST_OVERFLOWS_TYPE(u64, s8, S8_MAX, false); + TEST_OVERFLOWS_TYPE(u64, s8, (u64)S8_MAX + 1, true); + TEST_OVERFLOWS_TYPE(u64, s8, U64_MAX, true); + TEST_OVERFLOWS_TYPE(u64, s16, S16_MAX, false); + TEST_OVERFLOWS_TYPE(u64, s16, (u64)S16_MAX + 1, true); + TEST_OVERFLOWS_TYPE(u64, s16, U64_MAX, true); + TEST_OVERFLOWS_TYPE(u64, s32, S32_MAX, false); + TEST_OVERFLOWS_TYPE(u64, s32, (u64)S32_MAX + 1, true); + TEST_OVERFLOWS_TYPE(u64, s32, U64_MAX, true); + TEST_OVERFLOWS_TYPE(u64, s64, S64_MAX, false); + TEST_OVERFLOWS_TYPE(u64, s64, U64_MAX, true); + TEST_OVERFLOWS_TYPE(u64, s64, (u64)S64_MAX + 1, true); + TEST_OVERFLOWS_TYPE(s64, u8, S64_MAX, true); + TEST_OVERFLOWS_TYPE(s64, u8, S64_MIN, true); + TEST_OVERFLOWS_TYPE(s64, u8, -1, true); + TEST_OVERFLOWS_TYPE(s64, u8, U8_MAX, false); + TEST_OVERFLOWS_TYPE(s64, u8, (s64)U8_MAX + 1, true); + TEST_OVERFLOWS_TYPE(s64, u16, S64_MAX, true); + TEST_OVERFLOWS_TYPE(s64, u16, S64_MIN, true); + TEST_OVERFLOWS_TYPE(s64, u16, -1, true); + TEST_OVERFLOWS_TYPE(s64, u16, U16_MAX, false); + TEST_OVERFLOWS_TYPE(s64, u16, (s64)U16_MAX + 1, true); + TEST_OVERFLOWS_TYPE(s64, u32, S64_MAX, true); + TEST_OVERFLOWS_TYPE(s64, u32, S64_MIN, true); + TEST_OVERFLOWS_TYPE(s64, u32, -1, true); + TEST_OVERFLOWS_TYPE(s64, u32, U32_MAX, false); + TEST_OVERFLOWS_TYPE(s64, u32, (s64)U32_MAX + 1, true); + TEST_OVERFLOWS_TYPE(s64, u64, S64_MAX, false); + TEST_OVERFLOWS_TYPE(s64, u64, S64_MIN, true); + TEST_OVERFLOWS_TYPE(s64, u64, -1, true); + TEST_OVERFLOWS_TYPE(s64, s8, S8_MAX, false); + TEST_OVERFLOWS_TYPE(s64, s8, S8_MIN, false); + TEST_OVERFLOWS_TYPE(s64, s8, (s64)S8_MAX + 1, true); + TEST_OVERFLOWS_TYPE(s64, s8, (s64)S8_MIN - 1, true); + TEST_OVERFLOWS_TYPE(s64, s8, S64_MAX, true); + TEST_OVERFLOWS_TYPE(s64, s16, S16_MAX, false); + TEST_OVERFLOWS_TYPE(s64, s16, S16_MIN, false); + TEST_OVERFLOWS_TYPE(s64, s16, (s64)S16_MAX + 1, true); + TEST_OVERFLOWS_TYPE(s64, s16, (s64)S16_MIN - 1, true); + TEST_OVERFLOWS_TYPE(s64, s16, S64_MAX, true); + TEST_OVERFLOWS_TYPE(s64, s32, S32_MAX, false); + TEST_OVERFLOWS_TYPE(s64, s32, S32_MIN, false); + TEST_OVERFLOWS_TYPE(s64, s32, (s64)S32_MAX + 1, true); + TEST_OVERFLOWS_TYPE(s64, s32, (s64)S32_MIN - 1, true); + TEST_OVERFLOWS_TYPE(s64, s32, S64_MAX, true); + TEST_OVERFLOWS_TYPE(s64, s64, S64_MAX, false); + TEST_OVERFLOWS_TYPE(s64, s64, S64_MIN, false); +#endif + + /* Check for macro side-effects. */ + var = INT_MAX - 1; + __TEST_OVERFLOWS_TYPE(__overflows_type, var++, int, false); + __TEST_OVERFLOWS_TYPE(__overflows_type, var++, int, false); + __TEST_OVERFLOWS_TYPE(__overflows_type, var++, int, true); + var = INT_MAX - 1; + __TEST_OVERFLOWS_TYPE(overflows_type, var++, int, false); + __TEST_OVERFLOWS_TYPE(overflows_type, var++, int, false); + __TEST_OVERFLOWS_TYPE(overflows_type, var++, int, true); + + kunit_info(test, "%d overflows_type() tests finished\n", count); +#undef TEST_OVERFLOWS_TYPE +#undef __TEST_OVERFLOWS_TYPE +} + +static void same_type_test(struct kunit *test) +{ + int count = 0; + int var; + +#define TEST_SAME_TYPE(t1, t2, same) do { \ + typeof(t1) __t1h = type_max(t1); \ + typeof(t1) __t1l = type_min(t1); \ + typeof(t2) __t2h = type_max(t2); \ + typeof(t2) __t2l = type_min(t2); \ + KUNIT_EXPECT_EQ(test, true, __same_type(t1, __t1h)); \ + KUNIT_EXPECT_EQ(test, true, __same_type(t1, __t1l)); \ + KUNIT_EXPECT_EQ(test, true, __same_type(__t1h, t1)); \ + KUNIT_EXPECT_EQ(test, true, __same_type(__t1l, t1)); \ + KUNIT_EXPECT_EQ(test, true, __same_type(t2, __t2h)); \ + KUNIT_EXPECT_EQ(test, true, __same_type(t2, __t2l)); \ + KUNIT_EXPECT_EQ(test, true, __same_type(__t2h, t2)); \ + KUNIT_EXPECT_EQ(test, true, __same_type(__t2l, t2)); \ + KUNIT_EXPECT_EQ(test, same, __same_type(t1, t2)); \ + KUNIT_EXPECT_EQ(test, same, __same_type(t2, __t1h)); \ + KUNIT_EXPECT_EQ(test, same, __same_type(t2, __t1l)); \ + KUNIT_EXPECT_EQ(test, same, __same_type(__t1h, t2)); \ + KUNIT_EXPECT_EQ(test, same, __same_type(__t1l, t2)); \ + KUNIT_EXPECT_EQ(test, same, __same_type(t1, __t2h)); \ + KUNIT_EXPECT_EQ(test, same, __same_type(t1, __t2l)); \ + KUNIT_EXPECT_EQ(test, same, __same_type(__t2h, t1)); \ + KUNIT_EXPECT_EQ(test, same, __same_type(__t2l, t1)); \ +} while (0) + +#if BITS_PER_LONG == 64 +# define TEST_SAME_TYPE64(base, t, m) TEST_SAME_TYPE(base, t, m) +#else +# define TEST_SAME_TYPE64(base, t, m) do { } while (0) +#endif + +#define TEST_TYPE_SETS(base, mu8, mu16, mu32, ms8, ms16, ms32, mu64, ms64) \ +do { \ + TEST_SAME_TYPE(base, u8, mu8); \ + TEST_SAME_TYPE(base, u16, mu16); \ + TEST_SAME_TYPE(base, u32, mu32); \ + TEST_SAME_TYPE(base, s8, ms8); \ + TEST_SAME_TYPE(base, s16, ms16); \ + TEST_SAME_TYPE(base, s32, ms32); \ + TEST_SAME_TYPE64(base, u64, mu64); \ + TEST_SAME_TYPE64(base, s64, ms64); \ +} while (0) + + TEST_TYPE_SETS(u8, true, false, false, false, false, false, false, false); + TEST_TYPE_SETS(u16, false, true, false, false, false, false, false, false); + TEST_TYPE_SETS(u32, false, false, true, false, false, false, false, false); + TEST_TYPE_SETS(s8, false, false, false, true, false, false, false, false); + TEST_TYPE_SETS(s16, false, false, false, false, true, false, false, false); + TEST_TYPE_SETS(s32, false, false, false, false, false, true, false, false); +#if BITS_PER_LONG == 64 + TEST_TYPE_SETS(u64, false, false, false, false, false, false, true, false); + TEST_TYPE_SETS(s64, false, false, false, false, false, false, false, true); +#endif + + /* Check for macro side-effects. */ + var = 4; + KUNIT_EXPECT_EQ(test, var, 4); + KUNIT_EXPECT_TRUE(test, __same_type(var++, int)); + KUNIT_EXPECT_EQ(test, var, 4); + KUNIT_EXPECT_TRUE(test, __same_type(int, var++)); + KUNIT_EXPECT_EQ(test, var, 4); + KUNIT_EXPECT_TRUE(test, __same_type(var++, var++)); + KUNIT_EXPECT_EQ(test, var, 4); + + kunit_info(test, "%d __same_type() tests finished\n", count); + +#undef TEST_TYPE_SETS +#undef TEST_SAME_TYPE64 +#undef TEST_SAME_TYPE +} + +static void castable_to_type_test(struct kunit *test) +{ +#if BITS_PER_LONG == 64 + u64 big; + s64 small; +#else + u32 big; + s32 small; +#endif + int count = 0; + +#define TEST_CASTABLE_TO_TYPE(arg1, arg2, pass) do { \ + bool __pass = __castable_to_type(arg1, arg2); \ + KUNIT_EXPECT_EQ_MSG(test, __pass, pass, \ + "expected __castable_to_type(" #arg1 ", " #arg2 ") to%s pass\n",\ + pass ? "" : " not"); \ + count++; \ +} while (0) + + TEST_CASTABLE_TO_TYPE(16, u8, true); + TEST_CASTABLE_TO_TYPE(16, u16, true); + TEST_CASTABLE_TO_TYPE(16, u32, true); + TEST_CASTABLE_TO_TYPE(16, s8, true); + TEST_CASTABLE_TO_TYPE(16, s16, true); + TEST_CASTABLE_TO_TYPE(16, s32, true); + TEST_CASTABLE_TO_TYPE(-16, s8, true); + TEST_CASTABLE_TO_TYPE(-16, s16, true); + TEST_CASTABLE_TO_TYPE(-16, s32, true); +#if BITS_PER_LONG == 64 + TEST_CASTABLE_TO_TYPE(16, u64, true); + TEST_CASTABLE_TO_TYPE(-16, s64, true); +#endif + +#define TEST_CASTABLE_TO_TYPE_VAR(width) do { \ + u ## width u ## width ## var = 0; \ + s ## width s ## width ## var = 0; \ + \ + /* Constant expressions that fit types. */ \ + TEST_CASTABLE_TO_TYPE(type_max(u ## width), u ## width, true); \ + TEST_CASTABLE_TO_TYPE(type_min(u ## width), u ## width, true); \ + TEST_CASTABLE_TO_TYPE(type_max(u ## width), u ## width ## var, true); \ + TEST_CASTABLE_TO_TYPE(type_min(u ## width), u ## width ## var, true); \ + TEST_CASTABLE_TO_TYPE(type_max(s ## width), s ## width, true); \ + TEST_CASTABLE_TO_TYPE(type_min(s ## width), s ## width, true); \ + TEST_CASTABLE_TO_TYPE(type_max(s ## width), s ## width ## var, true); \ + TEST_CASTABLE_TO_TYPE(type_min(u ## width), s ## width ## var, true); \ + /* Constant expressions that do not fit types. */ \ + TEST_CASTABLE_TO_TYPE(type_max(u ## width), s ## width, false); \ + TEST_CASTABLE_TO_TYPE(type_max(u ## width), s ## width ## var, false); \ + TEST_CASTABLE_TO_TYPE(type_min(s ## width), u ## width, false); \ + TEST_CASTABLE_TO_TYPE(type_min(s ## width), u ## width ## var, false); \ + /* Non-constant expression with mismatched type. */ \ + TEST_CASTABLE_TO_TYPE(s ## width ## var, u ## width, false); \ + TEST_CASTABLE_TO_TYPE(u ## width ## var, s ## width, false); \ +} while (0) + +#define TEST_CASTABLE_TO_TYPE_RANGE(width) do { \ + unsigned long big = U ## width ## _MAX; \ + signed long small = S ## width ## _MIN; \ + u ## width u ## width ## var = 0; \ + s ## width s ## width ## var = 0; \ + \ + /* Constant expression in range. */ \ + TEST_CASTABLE_TO_TYPE(U ## width ## _MAX, u ## width, true); \ + TEST_CASTABLE_TO_TYPE(U ## width ## _MAX, u ## width ## var, true); \ + TEST_CASTABLE_TO_TYPE(S ## width ## _MIN, s ## width, true); \ + TEST_CASTABLE_TO_TYPE(S ## width ## _MIN, s ## width ## var, true); \ + /* Constant expression out of range. */ \ + TEST_CASTABLE_TO_TYPE((unsigned long)U ## width ## _MAX + 1, u ## width, false); \ + TEST_CASTABLE_TO_TYPE((unsigned long)U ## width ## _MAX + 1, u ## width ## var, false); \ + TEST_CASTABLE_TO_TYPE((signed long)S ## width ## _MIN - 1, s ## width, false); \ + TEST_CASTABLE_TO_TYPE((signed long)S ## width ## _MIN - 1, s ## width ## var, false); \ + /* Non-constant expression with mismatched type. */ \ + TEST_CASTABLE_TO_TYPE(big, u ## width, false); \ + TEST_CASTABLE_TO_TYPE(big, u ## width ## var, false); \ + TEST_CASTABLE_TO_TYPE(small, s ## width, false); \ + TEST_CASTABLE_TO_TYPE(small, s ## width ## var, false); \ +} while (0) + + TEST_CASTABLE_TO_TYPE_VAR(8); + TEST_CASTABLE_TO_TYPE_VAR(16); + TEST_CASTABLE_TO_TYPE_VAR(32); +#if BITS_PER_LONG == 64 + TEST_CASTABLE_TO_TYPE_VAR(64); +#endif + + TEST_CASTABLE_TO_TYPE_RANGE(8); + TEST_CASTABLE_TO_TYPE_RANGE(16); +#if BITS_PER_LONG == 64 + TEST_CASTABLE_TO_TYPE_RANGE(32); +#endif + kunit_info(test, "%d __castable_to_type() tests finished\n", count); + +#undef TEST_CASTABLE_TO_TYPE_RANGE +#undef TEST_CASTABLE_TO_TYPE_VAR +#undef TEST_CASTABLE_TO_TYPE +} + static struct kunit_case overflow_test_cases[] = { KUNIT_CASE(u8_u8__u8_overflow_test), KUNIT_CASE(s8_s8__s8_overflow_test), @@ -730,6 +1118,9 @@ static struct kunit_case overflow_test_cases[] = { KUNIT_CASE(shift_nonsense_test), KUNIT_CASE(overflow_allocation_test), KUNIT_CASE(overflow_size_helpers_test), + KUNIT_CASE(overflows_type_test), + KUNIT_CASE(same_type_test), + KUNIT_CASE(castable_to_type_test), {} }; -- 2.34.1 ^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v11.5] overflow: Introduce overflows_type() and __castable_to_type() 2022-09-26 0:37 ` [PATCH v11.5] overflow: Introduce overflows_type() and __castable_to_type() Kees Cook @ 2022-09-26 9:53 ` Gwan-gyeong Mun 2022-09-26 15:57 ` Gwan-gyeong Mun 1 sibling, 0 replies; 4+ messages in thread From: Gwan-gyeong Mun @ 2022-09-26 9:53 UTC (permalink / raw) To: Kees Cook Cc: Luc Van Oostenryck, Nathan Chancellor, Nick Desaulniers, Tom Rix, Daniel Latypov, Vitor Massaru Iha, Gustavo A. R. Silva, linux-hardening, llvm, intel-gfx, linux-kernel, dri-devel, mchehab, chris, matthew.auld, thomas.hellstrom, jani.nikula, nirmoy.das, airlied, daniel, andi.shyti, andrzej.hajda, mauro.chehab, linux, linux-sparse Hi Kees, Thank you so much for taking the time to refine and update the code and checking out where the side effects that I missed may occur. On 9/26/22 3:37 AM, Kees Cook wrote: > Add overflows_type() to test if a variable or constant value would > overflow another variable or type. This can be used as a constant > expression for static_assert() (which requires a constant > expression[1][2]) when used on constant values. This must be constructed > manually, since __builtin_add_overflow() does not produce a constant > expression[3]. > > Additionally adds __castable_to_type(), similar to __same_type(), for > checking if a constant value will fit in a given type (i.e. it could > be cast to the type without overflow). > > Add unit tests for overflows_type(), __same_type(), and > __castable_to_type() to the existing KUnit "overflow" test. > > [1] https://en.cppreference.com/w/c/language/_Static_assert > [2] C11 standard (ISO/IEC 9899:2011): 6.7.10 Static assertions > [3] https://gcc.gnu.org/onlinedocs/gcc/Integer-Overflow-Builtins.html > 6.56 Built-in Functions to Perform Arithmetic with Overflow Checking > Built-in Function: bool __builtin_add_overflow (type1 a, type2 b, > type3 *res) > > Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com> > Cc: Nathan Chancellor <nathan@kernel.org> > Cc: Nick Desaulniers <ndesaulniers@google.com> > Cc: Tom Rix <trix@redhat.com> > Cc: Daniel Latypov <dlatypov@google.com> > Cc: Vitor Massaru Iha <vitor@massaru.org> > Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org> > Cc: linux-hardening@vger.kernel.org > Cc: llvm@lists.linux.dev > Co-developed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com> > Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com> > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > include/linux/compiler.h | 1 + > include/linux/overflow.h | 48 +++++ > lib/overflow_kunit.c | 393 ++++++++++++++++++++++++++++++++++++++- > 3 files changed, 441 insertions(+), 1 deletion(-) > > diff --git a/include/linux/compiler.h b/include/linux/compiler.h > index 7713d7bcdaea..c631107e93b1 100644 > --- a/include/linux/compiler.h > +++ b/include/linux/compiler.h > @@ -244,6 +244,7 @@ static inline void *offset_to_ptr(const int *off) > * bool and also pointer types. > */ > #define is_signed_type(type) (((type)(-1)) < (__force type)1) > +#define is_unsigned_type(type) (!is_signed_type(type)) > > /* > * This is needed in functions which generate the stack canary, see > diff --git a/include/linux/overflow.h b/include/linux/overflow.h > index 19dfdd74835e..c8cbeae5f4f8 100644 > --- a/include/linux/overflow.h > +++ b/include/linux/overflow.h > @@ -127,6 +127,54 @@ static inline bool __must_check __must_check_overflow(bool overflow) > (*_d >> _to_shift) != _a); \ > })) > > +#define __overflows_type_constexpr(x, T) ( \ > + is_unsigned_type(typeof(x)) ? \ > + (x) > type_max(typeof(T)) ? 1 : 0 \ > + : is_unsigned_type(typeof(T)) ? \ > + (x) < 0 || (x) > type_max(typeof(T)) ? 1 : 0 \ > + : (x) < type_min(typeof(T)) || \ > + (x) > type_max(typeof(T)) ? 1 : 0 ) > + > +#define __overflows_type(x, T) ({ \ > + typeof(T) v = 0; \ > + check_add_overflow((x), v, &v); \ > +}) > + > +/** > + * overflows_type - helper for checking the overflows between value, variables, > + * or data type > + * > + * @n: source constant value or variable to be checked > + * @T: destination variable or data type proposed to store @x > + * > + * Compares the @x expression for whether or not it can safely fit in > + * the storage of the type in @T. @x and @T can have different types. > + * If @x is a conxtant expression, this will also resolve to a constant conxtant -> constant > + * expression. > + * > + * Returns: true if overflow can occur, false otherwise. > + */ > +#define overflows_type(n, T) \ > + __builtin_choose_expr(__is_constexpr(n), \ > + __overflows_type_constexpr(n, T), \ > + __overflows_type(n, T)) > + Did you do it because __overflows_type_constexpr() always requires __is_constexpr() to avoid side effects? And is the purpose of this macro to return a const-expression when a constant value is used as an argument and return a bool value when the argument is not a constant value? One more, to fix the build problem, the overflows_type() part added from this link (https://patchwork.freedesktop.org/patch/504377/?series=108945&rev=2) should be removed from this patch. And in other parts of this series, places that use macros added in a previous patch should also be updated. I'll fix those codes and send it as a new version. Many thanks, G.G. > +/** > + * __castable_to_type - like __same_type(), but also allows for casted literals > + * > + * @n: variable or constant value > + * @T: data type or variable > + * > + * Unlike the __same_type() macro, this allows a constant value as the > + * first argument. If this value would not overflow into an assignment > + * of the second argument's type, it returns true. Otherwise, this falls > + * back to __same_type(). > + */ > +#define __castable_to_type(n, T) \ > + __builtin_choose_expr(__is_constexpr(n), \ > + !__overflows_type_constexpr(n, T), \ > + __same_type(n, T)) > + > /** > * size_mul() - Calculate size_t multiplication with saturation at SIZE_MAX > * > diff --git a/lib/overflow_kunit.c b/lib/overflow_kunit.c > index f385ca652b74..9331d6ce914e 100644 > --- a/lib/overflow_kunit.c > +++ b/lib/overflow_kunit.c > @@ -16,6 +16,9 @@ > #include <linux/types.h> > #include <linux/vmalloc.h> > > +/* We're expecting to do a lot of "always true" or "always false" tests. */ > +#pragma clang diagnostic ignored "-Wtautological-constant-out-of-range-compare" > + > #define DEFINE_TEST_ARRAY_TYPED(t1, t2, t) \ > static const struct test_ ## t1 ## _ ## t2 ## __ ## t { \ > t1 a; \ > @@ -246,7 +249,7 @@ DEFINE_TEST_ARRAY(s64) = { > > #define DEFINE_TEST_FUNC_TYPED(n, t, fmt) \ > static void do_test_ ## n(struct kunit *test, const struct test_ ## n *p) \ > -{ \ > +{ \ > check_one_op(t, fmt, add, "+", p->a, p->b, p->sum, p->s_of); \ > check_one_op(t, fmt, add, "+", p->b, p->a, p->sum, p->s_of); \ > check_one_op(t, fmt, sub, "-", p->a, p->b, p->diff, p->d_of); \ > @@ -708,6 +711,391 @@ static void overflow_size_helpers_test(struct kunit *test) > #undef check_one_size_helper > } > > +static void overflows_type_test(struct kunit *test) > +{ > + int count = 0; > + unsigned int var; > + > +#define __TEST_OVERFLOWS_TYPE(func, arg1, arg2, of) do { \ > + bool __of = func(arg1, arg2); \ > + KUNIT_EXPECT_EQ_MSG(test, __of, of, \ > + "expected " #func "(" #arg1 ", " #arg2 " to%s overflow\n",\ > + of ? "" : " not"); \ > + count++; \ > +} while (0) > + > +/* Args are: first type, second type, value, overflow expected */ > +#define TEST_OVERFLOWS_TYPE(__t1, __t2, v, of) do { \ > + __t1 t1 = (v); \ > + __t2 t2; \ > + __TEST_OVERFLOWS_TYPE(__overflows_type, t1, t2, of); \ > + __TEST_OVERFLOWS_TYPE(__overflows_type, t1, __t2, of); \ > + __TEST_OVERFLOWS_TYPE(__overflows_type_constexpr, t1, t2, of); \ > + __TEST_OVERFLOWS_TYPE(__overflows_type_constexpr, t1, __t2, of);\ > +} while (0) > + > + TEST_OVERFLOWS_TYPE(u8, u8, U8_MAX, false); > + TEST_OVERFLOWS_TYPE(u8, u16, U8_MAX, false); > + TEST_OVERFLOWS_TYPE(u8, s8, U8_MAX, true); > + TEST_OVERFLOWS_TYPE(u8, s8, S8_MAX, false); > + TEST_OVERFLOWS_TYPE(u8, s8, (u8)S8_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(u8, s16, U8_MAX, false); > + TEST_OVERFLOWS_TYPE(s8, u8, S8_MAX, false); > + TEST_OVERFLOWS_TYPE(s8, u8, -1, true); > + TEST_OVERFLOWS_TYPE(s8, u8, S8_MIN, true); > + TEST_OVERFLOWS_TYPE(s8, u16, S8_MAX, false); > + TEST_OVERFLOWS_TYPE(s8, u16, -1, true); > + TEST_OVERFLOWS_TYPE(s8, u16, S8_MIN, true); > + TEST_OVERFLOWS_TYPE(s8, u32, S8_MAX, false); > + TEST_OVERFLOWS_TYPE(s8, u32, -1, true); > + TEST_OVERFLOWS_TYPE(s8, u32, S8_MIN, true); > +#if BITS_PER_LONG == 64 > + TEST_OVERFLOWS_TYPE(s8, u64, S8_MAX, false); > + TEST_OVERFLOWS_TYPE(s8, u64, -1, true); > + TEST_OVERFLOWS_TYPE(s8, u64, S8_MIN, true); > +#endif > + TEST_OVERFLOWS_TYPE(s8, s8, S8_MAX, false); > + TEST_OVERFLOWS_TYPE(s8, s8, S8_MIN, false); > + TEST_OVERFLOWS_TYPE(s8, s16, S8_MAX, false); > + TEST_OVERFLOWS_TYPE(s8, s16, S8_MIN, false); > + TEST_OVERFLOWS_TYPE(u16, u8, U8_MAX, false); > + TEST_OVERFLOWS_TYPE(u16, u8, (u16)U8_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(u16, u8, U16_MAX, true); > + TEST_OVERFLOWS_TYPE(u16, s8, S8_MAX, false); > + TEST_OVERFLOWS_TYPE(u16, s8, (u16)S8_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(u16, s8, U16_MAX, true); > + TEST_OVERFLOWS_TYPE(u16, s16, S16_MAX, false); > + TEST_OVERFLOWS_TYPE(u16, s16, (u16)S16_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(u16, s16, U16_MAX, true); > + TEST_OVERFLOWS_TYPE(u16, u32, U16_MAX, false); > + TEST_OVERFLOWS_TYPE(u16, s32, U16_MAX, false); > + TEST_OVERFLOWS_TYPE(s16, u8, U8_MAX, false); > + TEST_OVERFLOWS_TYPE(s16, u8, (s16)U8_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(s16, u8, -1, true); > + TEST_OVERFLOWS_TYPE(s16, u8, S16_MIN, true); > + TEST_OVERFLOWS_TYPE(s16, u16, S16_MAX, false); > + TEST_OVERFLOWS_TYPE(s16, u16, -1, true); > + TEST_OVERFLOWS_TYPE(s16, u16, S16_MIN, true); > + TEST_OVERFLOWS_TYPE(s16, u32, S16_MAX, false); > + TEST_OVERFLOWS_TYPE(s16, u32, -1, true); > + TEST_OVERFLOWS_TYPE(s16, u32, S16_MIN, true); > +#if BITS_PER_LONG == 64 > + TEST_OVERFLOWS_TYPE(s16, u64, S16_MAX, false); > + TEST_OVERFLOWS_TYPE(s16, u64, -1, true); > + TEST_OVERFLOWS_TYPE(s16, u64, S16_MIN, true); > +#endif > + TEST_OVERFLOWS_TYPE(s16, s8, S8_MAX, false); > + TEST_OVERFLOWS_TYPE(s16, s8, S8_MIN, false); > + TEST_OVERFLOWS_TYPE(s16, s8, (s16)S8_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(s16, s8, (s16)S8_MIN - 1, true); > + TEST_OVERFLOWS_TYPE(s16, s8, S16_MAX, true); > + TEST_OVERFLOWS_TYPE(s16, s8, S16_MIN, true); > + TEST_OVERFLOWS_TYPE(s16, s16, S16_MAX, false); > + TEST_OVERFLOWS_TYPE(s16, s16, S16_MIN, false); > + TEST_OVERFLOWS_TYPE(s16, s32, S16_MAX, false); > + TEST_OVERFLOWS_TYPE(s16, s32, S16_MIN, false); > + TEST_OVERFLOWS_TYPE(u32, u8, U8_MAX, false); > + TEST_OVERFLOWS_TYPE(u32, u8, (u32)U8_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(u32, u8, U32_MAX, true); > + TEST_OVERFLOWS_TYPE(u32, s8, S8_MAX, false); > + TEST_OVERFLOWS_TYPE(u32, s8, (u32)S8_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(u32, s8, U32_MAX, true); > + TEST_OVERFLOWS_TYPE(u32, u16, U16_MAX, false); > + TEST_OVERFLOWS_TYPE(u32, u16, U16_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(u32, u16, U32_MAX, true); > + TEST_OVERFLOWS_TYPE(u32, s16, S16_MAX, false); > + TEST_OVERFLOWS_TYPE(u32, s16, (u32)S16_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(u32, s16, U32_MAX, true); > + TEST_OVERFLOWS_TYPE(u32, u32, U32_MAX, false); > + TEST_OVERFLOWS_TYPE(u32, s32, S32_MAX, false); > + TEST_OVERFLOWS_TYPE(u32, s32, U32_MAX, true); > + TEST_OVERFLOWS_TYPE(u32, s32, (u32)S32_MAX + 1, true); > +#if BITS_PER_LONG == 64 > + TEST_OVERFLOWS_TYPE(u32, u64, U32_MAX, false); > + TEST_OVERFLOWS_TYPE(u32, s64, U32_MAX, false); > +#endif > + TEST_OVERFLOWS_TYPE(s32, u8, U8_MAX, false); > + TEST_OVERFLOWS_TYPE(s32, u8, (s32)U8_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(s32, u16, S32_MAX, true); > + TEST_OVERFLOWS_TYPE(s32, u8, -1, true); > + TEST_OVERFLOWS_TYPE(s32, u8, S32_MIN, true); > + TEST_OVERFLOWS_TYPE(s32, u16, U16_MAX, false); > + TEST_OVERFLOWS_TYPE(s32, u16, (s32)U16_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(s32, u16, S32_MAX, true); > + TEST_OVERFLOWS_TYPE(s32, u16, -1, true); > + TEST_OVERFLOWS_TYPE(s32, u16, S32_MIN, true); > + TEST_OVERFLOWS_TYPE(s32, u32, S32_MAX, false); > + TEST_OVERFLOWS_TYPE(s32, u32, -1, true); > + TEST_OVERFLOWS_TYPE(s32, u32, S32_MIN, true); > +#if BITS_PER_LONG == 64 > + TEST_OVERFLOWS_TYPE(s32, u64, S32_MAX, false); > + TEST_OVERFLOWS_TYPE(s32, u64, -1, true); > + TEST_OVERFLOWS_TYPE(s32, u64, S32_MIN, true); > +#endif > + TEST_OVERFLOWS_TYPE(s32, s8, S8_MAX, false); > + TEST_OVERFLOWS_TYPE(s32, s8, S8_MIN, false); > + TEST_OVERFLOWS_TYPE(s32, s8, (s32)S8_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(s32, s8, (s32)S8_MIN - 1, true); > + TEST_OVERFLOWS_TYPE(s32, s8, S32_MAX, true); > + TEST_OVERFLOWS_TYPE(s32, s8, S32_MIN, true); > + TEST_OVERFLOWS_TYPE(s32, s16, S16_MAX, false); > + TEST_OVERFLOWS_TYPE(s32, s16, S16_MIN, false); > + TEST_OVERFLOWS_TYPE(s32, s16, (s32)S16_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(s32, s16, (s32)S16_MIN - 1, true); > + TEST_OVERFLOWS_TYPE(s32, s16, S32_MAX, true); > + TEST_OVERFLOWS_TYPE(s32, s16, S32_MIN, true); > + TEST_OVERFLOWS_TYPE(s32, s32, S32_MAX, false); > + TEST_OVERFLOWS_TYPE(s32, s32, S32_MIN, false); > +#if BITS_PER_LONG == 64 > + TEST_OVERFLOWS_TYPE(s32, s64, S32_MAX, false); > + TEST_OVERFLOWS_TYPE(s32, s64, S32_MIN, false); > + TEST_OVERFLOWS_TYPE(u64, u8, U64_MAX, true); > + TEST_OVERFLOWS_TYPE(u64, u8, U8_MAX, false); > + TEST_OVERFLOWS_TYPE(u64, u8, (u64)U8_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(u64, u16, U64_MAX, true); > + TEST_OVERFLOWS_TYPE(u64, u16, U16_MAX, false); > + TEST_OVERFLOWS_TYPE(u64, u16, (u64)U16_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(u64, u32, U64_MAX, true); > + TEST_OVERFLOWS_TYPE(u64, u32, U32_MAX, false); > + TEST_OVERFLOWS_TYPE(u64, u32, (u64)U32_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(u64, u64, U64_MAX, false); > + TEST_OVERFLOWS_TYPE(u64, s8, S8_MAX, false); > + TEST_OVERFLOWS_TYPE(u64, s8, (u64)S8_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(u64, s8, U64_MAX, true); > + TEST_OVERFLOWS_TYPE(u64, s16, S16_MAX, false); > + TEST_OVERFLOWS_TYPE(u64, s16, (u64)S16_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(u64, s16, U64_MAX, true); > + TEST_OVERFLOWS_TYPE(u64, s32, S32_MAX, false); > + TEST_OVERFLOWS_TYPE(u64, s32, (u64)S32_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(u64, s32, U64_MAX, true); > + TEST_OVERFLOWS_TYPE(u64, s64, S64_MAX, false); > + TEST_OVERFLOWS_TYPE(u64, s64, U64_MAX, true); > + TEST_OVERFLOWS_TYPE(u64, s64, (u64)S64_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(s64, u8, S64_MAX, true); > + TEST_OVERFLOWS_TYPE(s64, u8, S64_MIN, true); > + TEST_OVERFLOWS_TYPE(s64, u8, -1, true); > + TEST_OVERFLOWS_TYPE(s64, u8, U8_MAX, false); > + TEST_OVERFLOWS_TYPE(s64, u8, (s64)U8_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(s64, u16, S64_MAX, true); > + TEST_OVERFLOWS_TYPE(s64, u16, S64_MIN, true); > + TEST_OVERFLOWS_TYPE(s64, u16, -1, true); > + TEST_OVERFLOWS_TYPE(s64, u16, U16_MAX, false); > + TEST_OVERFLOWS_TYPE(s64, u16, (s64)U16_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(s64, u32, S64_MAX, true); > + TEST_OVERFLOWS_TYPE(s64, u32, S64_MIN, true); > + TEST_OVERFLOWS_TYPE(s64, u32, -1, true); > + TEST_OVERFLOWS_TYPE(s64, u32, U32_MAX, false); > + TEST_OVERFLOWS_TYPE(s64, u32, (s64)U32_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(s64, u64, S64_MAX, false); > + TEST_OVERFLOWS_TYPE(s64, u64, S64_MIN, true); > + TEST_OVERFLOWS_TYPE(s64, u64, -1, true); > + TEST_OVERFLOWS_TYPE(s64, s8, S8_MAX, false); > + TEST_OVERFLOWS_TYPE(s64, s8, S8_MIN, false); > + TEST_OVERFLOWS_TYPE(s64, s8, (s64)S8_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(s64, s8, (s64)S8_MIN - 1, true); > + TEST_OVERFLOWS_TYPE(s64, s8, S64_MAX, true); > + TEST_OVERFLOWS_TYPE(s64, s16, S16_MAX, false); > + TEST_OVERFLOWS_TYPE(s64, s16, S16_MIN, false); > + TEST_OVERFLOWS_TYPE(s64, s16, (s64)S16_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(s64, s16, (s64)S16_MIN - 1, true); > + TEST_OVERFLOWS_TYPE(s64, s16, S64_MAX, true); > + TEST_OVERFLOWS_TYPE(s64, s32, S32_MAX, false); > + TEST_OVERFLOWS_TYPE(s64, s32, S32_MIN, false); > + TEST_OVERFLOWS_TYPE(s64, s32, (s64)S32_MAX + 1, true); > + TEST_OVERFLOWS_TYPE(s64, s32, (s64)S32_MIN - 1, true); > + TEST_OVERFLOWS_TYPE(s64, s32, S64_MAX, true); > + TEST_OVERFLOWS_TYPE(s64, s64, S64_MAX, false); > + TEST_OVERFLOWS_TYPE(s64, s64, S64_MIN, false); > +#endif > + > + /* Check for macro side-effects. */ > + var = INT_MAX - 1; > + __TEST_OVERFLOWS_TYPE(__overflows_type, var++, int, false); > + __TEST_OVERFLOWS_TYPE(__overflows_type, var++, int, false); > + __TEST_OVERFLOWS_TYPE(__overflows_type, var++, int, true); > + var = INT_MAX - 1; > + __TEST_OVERFLOWS_TYPE(overflows_type, var++, int, false); > + __TEST_OVERFLOWS_TYPE(overflows_type, var++, int, false); > + __TEST_OVERFLOWS_TYPE(overflows_type, var++, int, true); > + > + kunit_info(test, "%d overflows_type() tests finished\n", count); > +#undef TEST_OVERFLOWS_TYPE > +#undef __TEST_OVERFLOWS_TYPE > +} > + > +static void same_type_test(struct kunit *test) > +{ > + int count = 0; > + int var; > + > +#define TEST_SAME_TYPE(t1, t2, same) do { \ > + typeof(t1) __t1h = type_max(t1); \ > + typeof(t1) __t1l = type_min(t1); \ > + typeof(t2) __t2h = type_max(t2); \ > + typeof(t2) __t2l = type_min(t2); \ > + KUNIT_EXPECT_EQ(test, true, __same_type(t1, __t1h)); \ > + KUNIT_EXPECT_EQ(test, true, __same_type(t1, __t1l)); \ > + KUNIT_EXPECT_EQ(test, true, __same_type(__t1h, t1)); \ > + KUNIT_EXPECT_EQ(test, true, __same_type(__t1l, t1)); \ > + KUNIT_EXPECT_EQ(test, true, __same_type(t2, __t2h)); \ > + KUNIT_EXPECT_EQ(test, true, __same_type(t2, __t2l)); \ > + KUNIT_EXPECT_EQ(test, true, __same_type(__t2h, t2)); \ > + KUNIT_EXPECT_EQ(test, true, __same_type(__t2l, t2)); \ > + KUNIT_EXPECT_EQ(test, same, __same_type(t1, t2)); \ > + KUNIT_EXPECT_EQ(test, same, __same_type(t2, __t1h)); \ > + KUNIT_EXPECT_EQ(test, same, __same_type(t2, __t1l)); \ > + KUNIT_EXPECT_EQ(test, same, __same_type(__t1h, t2)); \ > + KUNIT_EXPECT_EQ(test, same, __same_type(__t1l, t2)); \ > + KUNIT_EXPECT_EQ(test, same, __same_type(t1, __t2h)); \ > + KUNIT_EXPECT_EQ(test, same, __same_type(t1, __t2l)); \ > + KUNIT_EXPECT_EQ(test, same, __same_type(__t2h, t1)); \ > + KUNIT_EXPECT_EQ(test, same, __same_type(__t2l, t1)); \ > +} while (0) > + > +#if BITS_PER_LONG == 64 > +# define TEST_SAME_TYPE64(base, t, m) TEST_SAME_TYPE(base, t, m) > +#else > +# define TEST_SAME_TYPE64(base, t, m) do { } while (0) > +#endif > + > +#define TEST_TYPE_SETS(base, mu8, mu16, mu32, ms8, ms16, ms32, mu64, ms64) \ > +do { \ > + TEST_SAME_TYPE(base, u8, mu8); \ > + TEST_SAME_TYPE(base, u16, mu16); \ > + TEST_SAME_TYPE(base, u32, mu32); \ > + TEST_SAME_TYPE(base, s8, ms8); \ > + TEST_SAME_TYPE(base, s16, ms16); \ > + TEST_SAME_TYPE(base, s32, ms32); \ > + TEST_SAME_TYPE64(base, u64, mu64); \ > + TEST_SAME_TYPE64(base, s64, ms64); \ > +} while (0) > + > + TEST_TYPE_SETS(u8, true, false, false, false, false, false, false, false); > + TEST_TYPE_SETS(u16, false, true, false, false, false, false, false, false); > + TEST_TYPE_SETS(u32, false, false, true, false, false, false, false, false); > + TEST_TYPE_SETS(s8, false, false, false, true, false, false, false, false); > + TEST_TYPE_SETS(s16, false, false, false, false, true, false, false, false); > + TEST_TYPE_SETS(s32, false, false, false, false, false, true, false, false); > +#if BITS_PER_LONG == 64 > + TEST_TYPE_SETS(u64, false, false, false, false, false, false, true, false); > + TEST_TYPE_SETS(s64, false, false, false, false, false, false, false, true); > +#endif > + > + /* Check for macro side-effects. */ > + var = 4; > + KUNIT_EXPECT_EQ(test, var, 4); > + KUNIT_EXPECT_TRUE(test, __same_type(var++, int)); > + KUNIT_EXPECT_EQ(test, var, 4); > + KUNIT_EXPECT_TRUE(test, __same_type(int, var++)); > + KUNIT_EXPECT_EQ(test, var, 4); > + KUNIT_EXPECT_TRUE(test, __same_type(var++, var++)); > + KUNIT_EXPECT_EQ(test, var, 4); > + > + kunit_info(test, "%d __same_type() tests finished\n", count); > + > +#undef TEST_TYPE_SETS > +#undef TEST_SAME_TYPE64 > +#undef TEST_SAME_TYPE > +} > + > +static void castable_to_type_test(struct kunit *test) > +{ > +#if BITS_PER_LONG == 64 > + u64 big; > + s64 small; > +#else > + u32 big; > + s32 small; > +#endif > + int count = 0; > + > +#define TEST_CASTABLE_TO_TYPE(arg1, arg2, pass) do { \ > + bool __pass = __castable_to_type(arg1, arg2); \ > + KUNIT_EXPECT_EQ_MSG(test, __pass, pass, \ > + "expected __castable_to_type(" #arg1 ", " #arg2 ") to%s pass\n",\ > + pass ? "" : " not"); \ > + count++; \ > +} while (0) > + > + TEST_CASTABLE_TO_TYPE(16, u8, true); > + TEST_CASTABLE_TO_TYPE(16, u16, true); > + TEST_CASTABLE_TO_TYPE(16, u32, true); > + TEST_CASTABLE_TO_TYPE(16, s8, true); > + TEST_CASTABLE_TO_TYPE(16, s16, true); > + TEST_CASTABLE_TO_TYPE(16, s32, true); > + TEST_CASTABLE_TO_TYPE(-16, s8, true); > + TEST_CASTABLE_TO_TYPE(-16, s16, true); > + TEST_CASTABLE_TO_TYPE(-16, s32, true); > +#if BITS_PER_LONG == 64 > + TEST_CASTABLE_TO_TYPE(16, u64, true); > + TEST_CASTABLE_TO_TYPE(-16, s64, true); > +#endif > + > +#define TEST_CASTABLE_TO_TYPE_VAR(width) do { \ > + u ## width u ## width ## var = 0; \ > + s ## width s ## width ## var = 0; \ > + \ > + /* Constant expressions that fit types. */ \ > + TEST_CASTABLE_TO_TYPE(type_max(u ## width), u ## width, true); \ > + TEST_CASTABLE_TO_TYPE(type_min(u ## width), u ## width, true); \ > + TEST_CASTABLE_TO_TYPE(type_max(u ## width), u ## width ## var, true); \ > + TEST_CASTABLE_TO_TYPE(type_min(u ## width), u ## width ## var, true); \ > + TEST_CASTABLE_TO_TYPE(type_max(s ## width), s ## width, true); \ > + TEST_CASTABLE_TO_TYPE(type_min(s ## width), s ## width, true); \ > + TEST_CASTABLE_TO_TYPE(type_max(s ## width), s ## width ## var, true); \ > + TEST_CASTABLE_TO_TYPE(type_min(u ## width), s ## width ## var, true); \ > + /* Constant expressions that do not fit types. */ \ > + TEST_CASTABLE_TO_TYPE(type_max(u ## width), s ## width, false); \ > + TEST_CASTABLE_TO_TYPE(type_max(u ## width), s ## width ## var, false); \ > + TEST_CASTABLE_TO_TYPE(type_min(s ## width), u ## width, false); \ > + TEST_CASTABLE_TO_TYPE(type_min(s ## width), u ## width ## var, false); \ > + /* Non-constant expression with mismatched type. */ \ > + TEST_CASTABLE_TO_TYPE(s ## width ## var, u ## width, false); \ > + TEST_CASTABLE_TO_TYPE(u ## width ## var, s ## width, false); \ > +} while (0) > + > +#define TEST_CASTABLE_TO_TYPE_RANGE(width) do { \ > + unsigned long big = U ## width ## _MAX; \ > + signed long small = S ## width ## _MIN; \ > + u ## width u ## width ## var = 0; \ > + s ## width s ## width ## var = 0; \ > + \ > + /* Constant expression in range. */ \ > + TEST_CASTABLE_TO_TYPE(U ## width ## _MAX, u ## width, true); \ > + TEST_CASTABLE_TO_TYPE(U ## width ## _MAX, u ## width ## var, true); \ > + TEST_CASTABLE_TO_TYPE(S ## width ## _MIN, s ## width, true); \ > + TEST_CASTABLE_TO_TYPE(S ## width ## _MIN, s ## width ## var, true); \ > + /* Constant expression out of range. */ \ > + TEST_CASTABLE_TO_TYPE((unsigned long)U ## width ## _MAX + 1, u ## width, false); \ > + TEST_CASTABLE_TO_TYPE((unsigned long)U ## width ## _MAX + 1, u ## width ## var, false); \ > + TEST_CASTABLE_TO_TYPE((signed long)S ## width ## _MIN - 1, s ## width, false); \ > + TEST_CASTABLE_TO_TYPE((signed long)S ## width ## _MIN - 1, s ## width ## var, false); \ > + /* Non-constant expression with mismatched type. */ \ > + TEST_CASTABLE_TO_TYPE(big, u ## width, false); \ > + TEST_CASTABLE_TO_TYPE(big, u ## width ## var, false); \ > + TEST_CASTABLE_TO_TYPE(small, s ## width, false); \ > + TEST_CASTABLE_TO_TYPE(small, s ## width ## var, false); \ > +} while (0) > + > + TEST_CASTABLE_TO_TYPE_VAR(8); > + TEST_CASTABLE_TO_TYPE_VAR(16); > + TEST_CASTABLE_TO_TYPE_VAR(32); > +#if BITS_PER_LONG == 64 > + TEST_CASTABLE_TO_TYPE_VAR(64); > +#endif > + > + TEST_CASTABLE_TO_TYPE_RANGE(8); > + TEST_CASTABLE_TO_TYPE_RANGE(16); > +#if BITS_PER_LONG == 64 > + TEST_CASTABLE_TO_TYPE_RANGE(32); > +#endif > + kunit_info(test, "%d __castable_to_type() tests finished\n", count); > + > +#undef TEST_CASTABLE_TO_TYPE_RANGE > +#undef TEST_CASTABLE_TO_TYPE_VAR > +#undef TEST_CASTABLE_TO_TYPE > +} > + > static struct kunit_case overflow_test_cases[] = { > KUNIT_CASE(u8_u8__u8_overflow_test), > KUNIT_CASE(s8_s8__s8_overflow_test), > @@ -730,6 +1118,9 @@ static struct kunit_case overflow_test_cases[] = { > KUNIT_CASE(shift_nonsense_test), > KUNIT_CASE(overflow_allocation_test), > KUNIT_CASE(overflow_size_helpers_test), > + KUNIT_CASE(overflows_type_test), > + KUNIT_CASE(same_type_test), > + KUNIT_CASE(castable_to_type_test), > {} > }; > ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v11.5] overflow: Introduce overflows_type() and __castable_to_type() 2022-09-26 0:37 ` [PATCH v11.5] overflow: Introduce overflows_type() and __castable_to_type() Kees Cook 2022-09-26 9:53 ` Gwan-gyeong Mun @ 2022-09-26 15:57 ` Gwan-gyeong Mun 2022-09-26 17:49 ` Kees Cook 1 sibling, 1 reply; 4+ messages in thread From: Gwan-gyeong Mun @ 2022-09-26 15:57 UTC (permalink / raw) To: Kees Cook Cc: Luc Van Oostenryck, Nathan Chancellor, Nick Desaulniers, Tom Rix, Daniel Latypov, Vitor Massaru Iha, Gustavo A. R. Silva, linux-hardening, llvm, intel-gfx, linux-kernel, dri-devel, mchehab, chris, matthew.auld, thomas.hellstrom, jani.nikula, nirmoy.das, airlied, daniel, andi.shyti, andrzej.hajda, mauro.chehab, linux, linux-sparse On 9/26/22 3:37 AM, Kees Cook wrote: > Add overflows_type() to test if a variable or constant value would > overflow another variable or type. This can be used as a constant > expression for static_assert() (which requires a constant > expression[1][2]) when used on constant values. This must be constructed > manually, since __builtin_add_overflow() does not produce a constant > expression[3]. > > Additionally adds __castable_to_type(), similar to __same_type(), for > checking if a constant value will fit in a given type (i.e. it could > be cast to the type without overflow). > > Add unit tests for overflows_type(), __same_type(), and > __castable_to_type() to the existing KUnit "overflow" test. > > [1] https://en.cppreference.com/w/c/language/_Static_assert > [2] C11 standard (ISO/IEC 9899:2011): 6.7.10 Static assertions > [3] https://gcc.gnu.org/onlinedocs/gcc/Integer-Overflow-Builtins.html > 6.56 Built-in Functions to Perform Arithmetic with Overflow Checking > Built-in Function: bool __builtin_add_overflow (type1 a, type2 b, > type3 *res) > > Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com> > Cc: Nathan Chancellor <nathan@kernel.org> > Cc: Nick Desaulniers <ndesaulniers@google.com> > Cc: Tom Rix <trix@redhat.com> > Cc: Daniel Latypov <dlatypov@google.com> > Cc: Vitor Massaru Iha <vitor@massaru.org> > Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org> > Cc: linux-hardening@vger.kernel.org > Cc: llvm@lists.linux.dev > Co-developed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com> > Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com> > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > include/linux/compiler.h | 1 + > include/linux/overflow.h | 48 +++++ > lib/overflow_kunit.c | 393 ++++++++++++++++++++++++++++++++++++++- > 3 files changed, 441 insertions(+), 1 deletion(-) > > diff --git a/include/linux/compiler.h b/include/linux/compiler.h > index 7713d7bcdaea..c631107e93b1 100644 > --- a/include/linux/compiler.h > +++ b/include/linux/compiler.h > @@ -244,6 +244,7 @@ static inline void *offset_to_ptr(const int *off) > * bool and also pointer types. > */ > #define is_signed_type(type) (((type)(-1)) < (__force type)1) > +#define is_unsigned_type(type) (!is_signed_type(type)) > > /* > * This is needed in functions which generate the stack canary, see > diff --git a/include/linux/overflow.h b/include/linux/overflow.h > index 19dfdd74835e..c8cbeae5f4f8 100644 > --- a/include/linux/overflow.h > +++ b/include/linux/overflow.h > @@ -127,6 +127,54 @@ static inline bool __must_check __must_check_overflow(bool overflow) > (*_d >> _to_shift) != _a); \ > })) > > +#define __overflows_type_constexpr(x, T) ( \ > + is_unsigned_type(typeof(x)) ? \ > + (x) > type_max(typeof(T)) ? 1 : 0 \ > + : is_unsigned_type(typeof(T)) ? \ > + (x) < 0 || (x) > type_max(typeof(T)) ? 1 : 0 \ > + : (x) < type_min(typeof(T)) || \ > + (x) > type_max(typeof(T)) ? 1 : 0 ) > + > +#define __overflows_type(x, T) ({ \ > + typeof(T) v = 0; \ > + check_add_overflow((x), v, &v); \ > +}) > + > +/** > + * overflows_type - helper for checking the overflows between value, variables, > + * or data type > + * > + * @n: source constant value or variable to be checked > + * @T: destination variable or data type proposed to store @x > + * > + * Compares the @x expression for whether or not it can safely fit in > + * the storage of the type in @T. @x and @T can have different types. > + * If @x is a conxtant expression, this will also resolve to a constant > + * expression. > + * > + * Returns: true if overflow can occur, false otherwise. > + */ > +#define overflows_type(n, T) \ > + __builtin_choose_expr(__is_constexpr(n), \ > + __overflows_type_constexpr(n, T), \ > + __overflows_type(n, T)) > + > +/** > + * __castable_to_type - like __same_type(), but also allows for casted literals > + * > + * @n: variable or constant value > + * @T: data type or variable > + * > + * Unlike the __same_type() macro, this allows a constant value as the > + * first argument. If this value would not overflow into an assignment > + * of the second argument's type, it returns true. Otherwise, this falls > + * back to __same_type(). > + */ > +#define __castable_to_type(n, T) \ > + __builtin_choose_expr(__is_constexpr(n), \ > + !__overflows_type_constexpr(n, T), \ > + __same_type(n, T)) > + This name is fine, but I prefer the __same_typable you suggested as a comment in the previous patch better, what do you think? ( __castable_to_type(n, T); The macro name seems to handle if type casting is possible to the second argument type from the first argument variable. ) G.G. ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v11.5] overflow: Introduce overflows_type() and __castable_to_type() 2022-09-26 15:57 ` Gwan-gyeong Mun @ 2022-09-26 17:49 ` Kees Cook 0 siblings, 0 replies; 4+ messages in thread From: Kees Cook @ 2022-09-26 17:49 UTC (permalink / raw) To: Gwan-gyeong Mun Cc: Luc Van Oostenryck, Nathan Chancellor, Nick Desaulniers, Tom Rix, Daniel Latypov, Vitor Massaru Iha, Gustavo A. R. Silva, linux-hardening, llvm, intel-gfx, linux-kernel, dri-devel, mchehab, chris, matthew.auld, thomas.hellstrom, jani.nikula, nirmoy.das, airlied, daniel, andi.shyti, andrzej.hajda, mauro.chehab, linux, linux-sparse On Mon, Sep 26, 2022 at 06:57:53PM +0300, Gwan-gyeong Mun wrote: > > > On 9/26/22 3:37 AM, Kees Cook wrote: > > Add overflows_type() to test if a variable or constant value would > > overflow another variable or type. This can be used as a constant > > expression for static_assert() (which requires a constant > > expression[1][2]) when used on constant values. This must be constructed > > manually, since __builtin_add_overflow() does not produce a constant > > expression[3]. > > > > Additionally adds __castable_to_type(), similar to __same_type(), for > > checking if a constant value will fit in a given type (i.e. it could > > be cast to the type without overflow). > > > > Add unit tests for overflows_type(), __same_type(), and > > __castable_to_type() to the existing KUnit "overflow" test. > > > > [1] https://en.cppreference.com/w/c/language/_Static_assert > > [2] C11 standard (ISO/IEC 9899:2011): 6.7.10 Static assertions > > [3] https://gcc.gnu.org/onlinedocs/gcc/Integer-Overflow-Builtins.html > > 6.56 Built-in Functions to Perform Arithmetic with Overflow Checking > > Built-in Function: bool __builtin_add_overflow (type1 a, type2 b, > > type3 *res) > > > > Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com> > > Cc: Nathan Chancellor <nathan@kernel.org> > > Cc: Nick Desaulniers <ndesaulniers@google.com> > > Cc: Tom Rix <trix@redhat.com> > > Cc: Daniel Latypov <dlatypov@google.com> > > Cc: Vitor Massaru Iha <vitor@massaru.org> > > Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org> > > Cc: linux-hardening@vger.kernel.org > > Cc: llvm@lists.linux.dev > > Co-developed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com> > > Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com> > > Signed-off-by: Kees Cook <keescook@chromium.org> > > --- > > include/linux/compiler.h | 1 + > > include/linux/overflow.h | 48 +++++ > > lib/overflow_kunit.c | 393 ++++++++++++++++++++++++++++++++++++++- > > 3 files changed, 441 insertions(+), 1 deletion(-) > > > > diff --git a/include/linux/compiler.h b/include/linux/compiler.h > > index 7713d7bcdaea..c631107e93b1 100644 > > --- a/include/linux/compiler.h > > +++ b/include/linux/compiler.h > > @@ -244,6 +244,7 @@ static inline void *offset_to_ptr(const int *off) > > * bool and also pointer types. > > */ > > #define is_signed_type(type) (((type)(-1)) < (__force type)1) > > +#define is_unsigned_type(type) (!is_signed_type(type)) > > /* > > * This is needed in functions which generate the stack canary, see > > diff --git a/include/linux/overflow.h b/include/linux/overflow.h > > index 19dfdd74835e..c8cbeae5f4f8 100644 > > --- a/include/linux/overflow.h > > +++ b/include/linux/overflow.h > > @@ -127,6 +127,54 @@ static inline bool __must_check __must_check_overflow(bool overflow) > > (*_d >> _to_shift) != _a); \ > > })) > > +#define __overflows_type_constexpr(x, T) ( \ > > + is_unsigned_type(typeof(x)) ? \ > > + (x) > type_max(typeof(T)) ? 1 : 0 \ > > + : is_unsigned_type(typeof(T)) ? \ > > + (x) < 0 || (x) > type_max(typeof(T)) ? 1 : 0 \ > > + : (x) < type_min(typeof(T)) || \ > > + (x) > type_max(typeof(T)) ? 1 : 0 ) > > + > > +#define __overflows_type(x, T) ({ \ > > + typeof(T) v = 0; \ > > + check_add_overflow((x), v, &v); \ > > +}) > > + > > +/** > > + * overflows_type - helper for checking the overflows between value, variables, > > + * or data type > > + * > > + * @n: source constant value or variable to be checked > > + * @T: destination variable or data type proposed to store @x > > + * > > + * Compares the @x expression for whether or not it can safely fit in > > + * the storage of the type in @T. @x and @T can have different types. > > + * If @x is a conxtant expression, this will also resolve to a constant > > + * expression. > > + * > > + * Returns: true if overflow can occur, false otherwise. > > + */ > > +#define overflows_type(n, T) \ > > + __builtin_choose_expr(__is_constexpr(n), \ > > + __overflows_type_constexpr(n, T), \ > > + __overflows_type(n, T)) > > + > > +/** > > + * __castable_to_type - like __same_type(), but also allows for casted literals > > + * > > + * @n: variable or constant value > > + * @T: data type or variable > > + * > > + * Unlike the __same_type() macro, this allows a constant value as the > > + * first argument. If this value would not overflow into an assignment > > + * of the second argument's type, it returns true. Otherwise, this falls > > + * back to __same_type(). > > + */ > > +#define __castable_to_type(n, T) \ > > + __builtin_choose_expr(__is_constexpr(n), \ > > + !__overflows_type_constexpr(n, T), \ > > + __same_type(n, T)) > > + > This name is fine, but I prefer the __same_typable you suggested as a > comment in the previous patch better, what do you think? > ( __castable_to_type(n, T); The macro name seems to handle if type casting > is possible to the second argument type from the first argument variable. ) I changed this name because "typable" isn't a familiar name for someone reading all of this for the first time. What's really happening is a check if _casting_ will result in an overflow. And when I named it just "__castable_type" it sounded like a declaration rather than a test. But perhaps it should lose the "__" prefix, and just be "castable_to_type"? Or even more verbose as "can_cast_to_type()" ? As for argument order, it seemed best to keep the order the same as with overflows_type(). I think that makes all of these macros a bit easier to read/review/understand for others. -- Kees Cook ^ permalink raw reply [flat|nested] 4+ messages in thread
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2022-09-26 0:37 ` [PATCH v11.5] overflow: Introduce overflows_type() and __castable_to_type() Kees Cook
2022-09-26 9:53 ` Gwan-gyeong Mun
2022-09-26 15:57 ` Gwan-gyeong Mun
2022-09-26 17:49 ` Kees Cook
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