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Date: Mon, 29 Aug 2022 13:47:29 -0700
From: Kees Cook <keescook@...omium.org>
To: Rasmus Villemoes <linux@...musvillemoes.dk>
Cc: Kees Cook <keescook@...omium.org>,
Gwan-gyeong Mun <gwan-gyeong.mun@...el.com>,
Andrzej Hajda <andrzej.hajda@...el.com>,
"Gustavo A. R. Silva" <gustavoars@...nel.org>,
Nick Desaulniers <ndesaulniers@...gle.com>,
linux-hardening@...r.kernel.org,
Daniel Latypov <dlatypov@...gle.com>,
Vitor Massaru Iha <vitor@...saru.org>,
linux-kernel@...r.kernel.org
Subject: [PATCH] overflow: Allow mixed type arguments
When the check_[op]_overflow() helpers were introduced, all arguments were
required to be the same type to make the fallback macros simpler. However,
once the fallback macros were 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.
[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@...musvillemoes.dk>
Cc: Gwan-gyeong Mun <gwan-gyeong.mun@...el.com>
Cc: Andrzej Hajda <andrzej.hajda@...el.com>
Cc: "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: Nick Desaulniers <ndesaulniers@...gle.com>
Cc: linux-hardening@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
include/linux/overflow.h | 6 ----
lib/overflow_kunit.c | 77 +++++++++++++++++++++++++++++-----------
2 files changed, 57 insertions(+), 26 deletions(-)
diff --git a/include/linux/overflow.h b/include/linux/overflow.h
index 0eb3b192f07a..ad692fb11bf3 100644
--- a/include/linux/overflow.h
+++ b/include/linux/overflow.h
@@ -63,8 +63,6 @@ static inline bool __must_check __must_check_overflow(bool 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); \
}))
@@ -72,8 +70,6 @@ static inline bool __must_check __must_check_overflow(bool 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); \
}))
@@ -81,8 +77,6 @@ static inline bool __must_check __must_check_overflow(bool 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); \
}))
diff --git a/lib/overflow_kunit.c b/lib/overflow_kunit.c
index 7e3e43679b73..ac771fe7e276 100644
--- a/lib/overflow_kunit.c
+++ b/lib/overflow_kunit.c
@@ -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},
@@ -235,8 +238,8 @@ DEFINE_TEST_ARRAY(s64) = {
a, b, r, _r, #t); \
} 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 +248,18 @@ 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 +271,33 @@ 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(u32u32u8, 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(u32u32int, 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(u8u8int, 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(intintu8, u8, "%d");
+
static void overflow_shift_test(struct kunit *test)
{
int count = 0;
@@ -649,17 +682,21 @@ 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(u8u8u8_overflow_test),
+ KUNIT_CASE(s8s8s8_overflow_test),
+ KUNIT_CASE(u16u16u16_overflow_test),
+ KUNIT_CASE(s16s16s16_overflow_test),
+ KUNIT_CASE(u32u32u32_overflow_test),
+ KUNIT_CASE(s32s32s32_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(u64u64u64_overflow_test),
+ KUNIT_CASE(s64s64s64_overflow_test),
#endif
+ KUNIT_CASE(u32u32u8_overflow_test),
+ KUNIT_CASE(u32u32int_overflow_test),
+ KUNIT_CASE(u8u8int_overflow_test),
+ KUNIT_CASE(intintu8_overflow_test),
KUNIT_CASE(overflow_shift_test),
KUNIT_CASE(overflow_allocation_test),
KUNIT_CASE(overflow_size_helpers_test),
--
2.34.1
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