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overflow: Allow mixed type arguments

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When the check_[op]_overflow() helpers were introduced, all arguments
were required to be the same type to make the fallback macros simpler.
However, now that the fallback macros have been removed[1], it is fine
to allow mixed types, which makes using the helpers much more useful,
as they can be used to test for type-based overflows (e.g. adding two
large ints but storing into a u8), as would be handy in the drm core[2].

Remove the restriction, and add additional self-tests that exercise
some of the mixed-type overflow cases, and double-check for accidental
macro side-effects.

[1] https://git.kernel.org/linus/4eb6bd55cfb22ffc20652732340c4962f3ac9a91
[2] https://lore.kernel.org/lkml/20220824084514.2261614-2-gwan-gyeong.mun@intel.com

Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: linux-hardening@vger.kernel.org
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Reviewed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Tested-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Kees Cook 2022-08-29 13:37:17 -07:00
parent 92d23c6e94
commit d219d2a9a9
2 changed files with 113 additions and 60 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

72
include/linux/overflow.h
View File

@ -51,40 +51,50 @@ static inline bool __must_check __must_check_overflow(bool overflow)
return unlikely(overflow);
}
/*
* For simplicity and code hygiene, the fallback code below insists on
* a, b and *d having the same type (similar to the min() and max()
* macros), whereas gcc's type-generic overflow checkers accept
* different types. Hence we don't just make check_add_overflow an
* alias for __builtin_add_overflow, but add type checks similar to
* below.
/** check_add_overflow() - Calculate addition with overflow checking
*
* @a: first addend
* @b: second addend
* @d: pointer to store sum
*
* Returns 0 on success.
*
* *@d holds the results of the attempted addition, but is not considered
* "safe for use" on a non-zero return value, which indicates that the
* sum has overflowed or been truncated.
*/
#define check_add_overflow(a, b, d) __must_check_overflow(({ \
typeof(a) __a = (a); \
typeof(b) __b = (b); \
typeof(d) __d = (d); \
(void) (&__a == &__b); \
(void) (&__a == __d); \
__builtin_add_overflow(__a, __b, __d); \
}))
#define check_add_overflow(a, b, d) \
__must_check_overflow(__builtin_add_overflow(a, b, d))
#define check_sub_overflow(a, b, d) __must_check_overflow(({ \
typeof(a) __a = (a); \
typeof(b) __b = (b); \
typeof(d) __d = (d); \
(void) (&__a == &__b); \
(void) (&__a == __d); \
__builtin_sub_overflow(__a, __b, __d); \
}))
/** check_sub_overflow() - Calculate subtraction with overflow checking
*
* @a: minuend; value to subtract from
* @b: subtrahend; value to subtract from @a
* @d: pointer to store difference
*
* Returns 0 on success.
*
* *@d holds the results of the attempted subtraction, but is not considered
* "safe for use" on a non-zero return value, which indicates that the
* difference has underflowed or been truncated.
*/
#define check_sub_overflow(a, b, d) \
__must_check_overflow(__builtin_sub_overflow(a, b, d))
#define check_mul_overflow(a, b, d) __must_check_overflow(({ \
typeof(a) __a = (a); \
typeof(b) __b = (b); \
typeof(d) __d = (d); \
(void) (&__a == &__b); \
(void) (&__a == __d); \
__builtin_mul_overflow(__a, __b, __d); \
}))
/** check_mul_overflow() - Calculate multiplication with overflow checking
*
* @a: first factor
* @b: second factor
* @d: pointer to store product
*
* Returns 0 on success.
*
* *@d holds the results of the attempted multiplication, but is not
* considered "safe for use" on a non-zero return value, which indicates
* that the product has overflowed or been truncated.
*/
#define check_mul_overflow(a, b, d) \
__must_check_overflow(__builtin_mul_overflow(a, b, d))
/** check_shl_overflow() - Calculate a left-shifted value and check overflow
*

101
lib/overflow_kunit.c
View File

@ -16,12 +16,15 @@
#include <linux/types.h>
#include <linux/vmalloc.h>
#define DEFINE_TEST_ARRAY(t) \
static const struct test_ ## t { \
t a, b; \
t sum, diff, prod; \
bool s_of, d_of, p_of; \
} t ## _tests[]
#define DEFINE_TEST_ARRAY_TYPED(t1, t2, t) \
static const struct test_ ## t1 ## _ ## t2 ## __ ## t { \
t1 a; \
t2 b; \
t sum, diff, prod; \
bool s_of, d_of, p_of; \
} t1 ## _ ## t2 ## __ ## t ## _tests[]
#define DEFINE_TEST_ARRAY(t) DEFINE_TEST_ARRAY_TYPED(t, t, t)
DEFINE_TEST_ARRAY(u8) = {
{0, 0, 0, 0, 0, false, false, false},
@ -222,21 +225,27 @@ DEFINE_TEST_ARRAY(s64) = {
};
#endif
#define check_one_op(t, fmt, op, sym, a, b, r, of) do { \
t _r; \
bool _of; \
\
_of = check_ ## op ## _overflow(a, b, &_r); \
KUNIT_EXPECT_EQ_MSG(test, _of, of, \
#define check_one_op(t, fmt, op, sym, a, b, r, of) do { \
int _a_orig = a, _a_bump = a + 1; \
int _b_orig = b, _b_bump = b + 1; \
bool _of; \
t _r; \
\
_of = check_ ## op ## _overflow(a, b, &_r); \
KUNIT_EXPECT_EQ_MSG(test, _of, of, \
"expected "fmt" "sym" "fmt" to%s overflow (type %s)\n", \
a, b, of ? "" : " not", #t); \
KUNIT_EXPECT_EQ_MSG(test, _r, r, \
a, b, of ? "" : " not", #t); \
KUNIT_EXPECT_EQ_MSG(test, _r, r, \
"expected "fmt" "sym" "fmt" == "fmt", got "fmt" (type %s)\n", \
a, b, r, _r, #t); \
a, b, r, _r, #t); \
/* Check for internal macro side-effects. */ \
_of = check_ ## op ## _overflow(_a_orig++, _b_orig++, &_r); \
KUNIT_EXPECT_EQ_MSG(test, _a_orig, _a_bump, "Unexpected " #op " macro side-effect!\n"); \
KUNIT_EXPECT_EQ_MSG(test, _b_orig, _b_bump, "Unexpected " #op " macro side-effect!\n"); \
} while (0)
#define DEFINE_TEST_FUNC(t, fmt) \
static void do_test_ ## t(struct kunit *test, const struct test_ ## t *p) \
#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); \
@ -245,15 +254,18 @@ static void do_test_ ## t(struct kunit *test, const struct test_ ## t *p) \
check_one_op(t, fmt, mul, "*", p->b, p->a, p->prod, p->p_of); \
} \
\
static void t ## _overflow_test(struct kunit *test) { \
static void n ## _overflow_test(struct kunit *test) { \
unsigned i; \
\
for (i = 0; i < ARRAY_SIZE(t ## _tests); ++i) \
do_test_ ## t(test, &t ## _tests[i]); \
for (i = 0; i < ARRAY_SIZE(n ## _tests); ++i) \
do_test_ ## n(test, &n ## _tests[i]); \
kunit_info(test, "%zu %s arithmetic tests finished\n", \
ARRAY_SIZE(t ## _tests), #t); \
ARRAY_SIZE(n ## _tests), #n); \
}
#define DEFINE_TEST_FUNC(t, fmt) \
DEFINE_TEST_FUNC_TYPED(t ## _ ## t ## __ ## t, t, fmt)
DEFINE_TEST_FUNC(u8, "%d");
DEFINE_TEST_FUNC(s8, "%d");
DEFINE_TEST_FUNC(u16, "%d");
@ -265,6 +277,33 @@ DEFINE_TEST_FUNC(u64, "%llu");
DEFINE_TEST_FUNC(s64, "%lld");
#endif
DEFINE_TEST_ARRAY_TYPED(u32, u32, u8) = {
{0, 0, 0, 0, 0, false, false, false},
{U8_MAX, 2, 1, U8_MAX - 2, U8_MAX - 1, true, false, true},
{U8_MAX + 1, 0, 0, 0, 0, true, true, false},
};
DEFINE_TEST_FUNC_TYPED(u32_u32__u8, u8, "%d");
DEFINE_TEST_ARRAY_TYPED(u32, u32, int) = {
{0, 0, 0, 0, 0, false, false, false},
{U32_MAX, 0, -1, -1, 0, true, true, false},
};
DEFINE_TEST_FUNC_TYPED(u32_u32__int, int, "%d");
DEFINE_TEST_ARRAY_TYPED(u8, u8, int) = {
{0, 0, 0, 0, 0, false, false, false},
{U8_MAX, U8_MAX, 2 * U8_MAX, 0, U8_MAX * U8_MAX, false, false, false},
{1, 2, 3, -1, 2, false, false, false},
};
DEFINE_TEST_FUNC_TYPED(u8_u8__int, int, "%d");
DEFINE_TEST_ARRAY_TYPED(int, int, u8) = {
{0, 0, 0, 0, 0, false, false, false},
{1, 2, 3, U8_MAX, 2, false, true, false},
{-1, 0, U8_MAX, U8_MAX, 0, true, true, false},
};
DEFINE_TEST_FUNC_TYPED(int_int__u8, u8, "%d");
static void overflow_shift_test(struct kunit *test)
{
int count = 0;
@ -649,17 +688,21 @@ static void overflow_size_helpers_test(struct kunit *test)
}
static struct kunit_case overflow_test_cases[] = {
KUNIT_CASE(u8_overflow_test),
KUNIT_CASE(s8_overflow_test),
KUNIT_CASE(u16_overflow_test),
KUNIT_CASE(s16_overflow_test),
KUNIT_CASE(u32_overflow_test),
KUNIT_CASE(s32_overflow_test),
KUNIT_CASE(u8_u8__u8_overflow_test),
KUNIT_CASE(s8_s8__s8_overflow_test),
KUNIT_CASE(u16_u16__u16_overflow_test),
KUNIT_CASE(s16_s16__s16_overflow_test),
KUNIT_CASE(u32_u32__u32_overflow_test),
KUNIT_CASE(s32_s32__s32_overflow_test),
/* Clang 13 and earlier generate unwanted libcalls on 32-bit. */
#if BITS_PER_LONG == 64
KUNIT_CASE(u64_overflow_test),
KUNIT_CASE(s64_overflow_test),
KUNIT_CASE(u64_u64__u64_overflow_test),
KUNIT_CASE(s64_s64__s64_overflow_test),
#endif
KUNIT_CASE(u32_u32__u8_overflow_test),
KUNIT_CASE(u32_u32__int_overflow_test),
KUNIT_CASE(u8_u8__int_overflow_test),
KUNIT_CASE(int_int__u8_overflow_test),
KUNIT_CASE(overflow_shift_test),
KUNIT_CASE(overflow_allocation_test),
KUNIT_CASE(overflow_size_helpers_test),