| Message ID | 20240123002814.1396804-1-keescook@chromium.org (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | overflow: Refactor open-coded arithmetic wrap-around | expand |
Hi, On Mon, Jan 22, 2024 at 04:26:36PM -0800, Kees Cook wrote: > The check_add_overflow() helper is mostly a wrapper around > __builtin_add_overflow(), but GCC and Clang refuse to operate on pointer > arguments that would normally be allowed if the addition were open-coded. > > For example, we have many places where pointer overflow is tested: > > struct foo *ptr; > ... > /* Check for overflow */ > if (ptr + count < ptr) ... > > And in order to avoid running into the overflow sanitizers in the > future, we need to rewrite these "intended" overflow checks: > > if (check_add_overflow(ptr, count, &result)) ... > > Frustratingly the argument type validation for __builtin_add_overflow() > is done before evaluating __builtin_choose_expr(), so for arguments to > be valid simultaneously for sizeof(*p) (when p may not be a pointer), > and __builtin_add_overflow(a, ...) (when a may be a pointer), we must > introduce wrappers that always produce a specific type (but they are > only used in the places where the bogus arguments will be ignored). > > To test whether a variable is a pointer or not, introduce the __is_ptr() > helper, which uses __builtin_classify_type() to find arrays and pointers > (via the new __is_ptr_or_array() helper), and then decays arrays into > pointers (via the new __decay() helper), to distinguish pointers from > arrays. > > Additionally update the unit tests to cover pointer addition. > > Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Nathan Chancellor <nathan@kernel.org> > Cc: Nick Desaulniers <ndesaulniers@google.com> > Cc: Bill Wendling <morbo@google.com> > Cc: Justin Stitt <justinstitt@google.com> > Cc: llvm@lists.linux.dev > Cc: linux-hardening@vger.kernel.org > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > include/linux/compiler_types.h | 10 +++++ > include/linux/overflow.h | 44 ++++++++++++++++++- > lib/overflow_kunit.c | 77 ++++++++++++++++++++++++++++++---- > 3 files changed, 121 insertions(+), 10 deletions(-) > > diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h > index 6f1ca49306d2..d27b58fddfaa 100644 > --- a/include/linux/compiler_types.h > +++ b/include/linux/compiler_types.h > @@ -375,6 +375,16 @@ struct ftrace_likely_data { > /* Are two types/vars the same type (ignoring qualifiers)? */ > #define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b)) > > +/* Is variable addressable? */ > +#define __is_ptr_or_array(p) (__builtin_classify_type(p) == 5) > + > +/* Return an array decayed to a pointer. */ > +#define __decay(p) \ > + (&*__builtin_choose_expr(__is_ptr_or_array(p), p, NULL)) Initially, I thought this __decay could dereference a NULL which would be UB. According to the C std 6.5.3.2 (4): | The unary * operator denotes indirection. If the operand points to a | function, the result is a function designator; if it points to an | object, the result is an lvalue designating the object. If the operand | has type ‘‘pointer to type’’, the result has type ‘‘type’’. If an | invalid value has been assigned to the pointer, the behavior of the | unary * operator is undefined^(84) With footnote 84 mentioning NULL: | Among the invalid values for dereferencing a pointer by the unary * | operator are a null pointer, an address inappropriately aligned for the | type of object pointed to, and the address of an object after the end of | its lifetime. However, in this very same footnote it mentions: | &*E is equivalent to E (even if E is a null pointer) So, yeah this is OK ( and new to me :>] ) > + > +/* Report if variable is a pointer type. */ > +#define __is_ptr(p) __same_type(p, __decay(p)) > + > /* > * __unqual_scalar_typeof(x) - Declare an unqualified scalar type, leaving > * non-scalar types unchanged. > diff --git a/include/linux/overflow.h b/include/linux/overflow.h > index 7b5cf4a5cd19..099f2e559aa8 100644 > --- a/include/linux/overflow.h > +++ b/include/linux/overflow.h > @@ -51,6 +51,45 @@ static inline bool __must_check __must_check_overflow(bool overflow) > return unlikely(overflow); > } > > +/* Always produce an integral variable expression. */ > +#define __filter_integral(x) \ > + __builtin_choose_expr(!__is_ptr(x), (x), 0) > + > +/* Always produce a pointer value. */ > +#define __filter_ptr(x) \ > + __builtin_choose_expr(__is_ptr(x), (x), NULL) > + > +/* Always produce a pointer to an integral value. */ > +#define __filter_ptrint(x) \ > + __builtin_choose_expr(!__is_ptr(*(x)), x, &(int){ 0 }) > + > +/** > + * __check_ptr_add_overflow() - Calculate pointer addition with overflow checking > + * @a: pointer addend > + * @b: numeric addend > + * @d: pointer to store sum > + * > + * Returns 0 on success. > + * > + * Do not use this function directly, use check_add_overflow() instead. > + * > + * *@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_ptr_add_overflow(a, b, d) \ > + ({ \ > + typeof(a) __a = (a); \ > + typeof(b) __b = (b); \ > + size_t __bytes; \ > + bool __overflow; \ > + \ > + /* we want to perform the wrap-around, but retain the result */ \ > + __overflow = __builtin_mul_overflow(sizeof(*(__a)), __b, &__bytes); \ > + __builtin_add_overflow((unsigned long)(__a), __bytes, (unsigned long *)(d)) || \ > + __overflow; \ > + }) > + > /** > * check_add_overflow() - Calculate addition with overflow checking > * @a: first addend > @@ -64,7 +103,10 @@ static inline bool __must_check __must_check_overflow(bool overflow) > * sum has overflowed or been truncated. > */ > #define check_add_overflow(a, b, d) \ > - __must_check_overflow(__builtin_add_overflow(a, b, d)) > + __must_check_overflow(__builtin_choose_expr(__is_ptr(a), \ > + __check_ptr_add_overflow(__filter_ptr(a), b, d), \ > + __builtin_add_overflow(__filter_integral(a), b, \ > + __filter_ptrint(d)))) > > /** > * check_sub_overflow() - Calculate subtraction with overflow checking Does check_sub_overflow() deserve some more love in the future? I imagine "under"-flowing pointers is not at all common, though. Nonetheless, this all looks good to me. Reviewed-by: Justin Stitt <justinstitt@google.com> > diff --git a/lib/overflow_kunit.c b/lib/overflow_kunit.c > index c527f6b75789..2d106e880956 100644 > --- a/lib/overflow_kunit.c > +++ b/lib/overflow_kunit.c > @@ -45,13 +45,18 @@ > # define SKIP_64_ON_32(t) do { } while (0) > #endif > > -#define DEFINE_TEST_ARRAY_TYPED(t1, t2, t) \ > - static const struct test_ ## t1 ## _ ## t2 ## __ ## t { \ > +#define DEFINE_TEST_ARRAY_NAMED_TYPED(n1, n2, n, t1, t2, t) \ > + static const struct test_ ## n1 ## _ ## n2 ## __ ## n { \ > t1 a; \ > t2 b; \ > - t sum, diff, prod; \ > + t sum; \ > + t diff; \ > + t prod; \ > bool s_of, d_of, p_of; \ > - } t1 ## _ ## t2 ## __ ## t ## _tests[] > + } n1 ## _ ## n2 ## __ ## n ## _tests[] > + > +#define DEFINE_TEST_ARRAY_TYPED(t1, t2, t) \ > + DEFINE_TEST_ARRAY_NAMED_TYPED(t1, t2, t, t1, t2, t) > > #define DEFINE_TEST_ARRAY(t) DEFINE_TEST_ARRAY_TYPED(t, t, t) > > @@ -251,8 +256,10 @@ DEFINE_TEST_ARRAY(s64) = { > }; > > #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; \ > + typeof(a + 0) _a_orig = a; \ > + typeof(a + 0) _a_bump = a + 1; \ > + typeof(b + 0) _b_orig = b; \ > + typeof(b + 0) _b_bump = b + 1; \ > bool _of; \ > t _r; \ > \ > @@ -260,13 +267,13 @@ DEFINE_TEST_ARRAY(s64) = { > 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, \ > + KUNIT_EXPECT_TRUE_MSG(test, _r == r, \ > "expected "fmt" "sym" "fmt" == "fmt", got "fmt" (type %s)\n", \ > 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"); \ > + KUNIT_EXPECT_TRUE_MSG(test, _a_orig == _a_bump, "Unexpected " #op " macro side-effect!\n"); \ > + KUNIT_EXPECT_TRUE_MSG(test, _b_orig == _b_bump, "Unexpected " #op " macro side-effect!\n"); \ > } while (0) > > #define DEFINE_TEST_FUNC_TYPED(n, t, fmt) \ > @@ -333,6 +340,55 @@ DEFINE_TEST_ARRAY_TYPED(int, int, u8) = { > }; > DEFINE_TEST_FUNC_TYPED(int_int__u8, u8, "%d"); > > +#define DEFINE_TEST_PTR_FUNC_TYPED(n, t, fmt) \ > +static void do_ptr_test_ ## n(struct kunit *test, const struct test_ ## n *p) \ > +{ \ > + /* we're only doing single-direction sums, no product or division */ \ > + check_one_op(t, fmt, add, "+", p->a, p->b, p->sum, p->s_of);\ > +} \ > + \ > +static void n ## _overflow_test(struct kunit *test) { \ > + unsigned i; \ > + \ > + for (i = 0; i < ARRAY_SIZE(n ## _tests); ++i) \ > + do_ptr_test_ ## n(test, &n ## _tests[i]); \ > + kunit_info(test, "%zu %s arithmetic tests finished\n", \ > + ARRAY_SIZE(n ## _tests), #n); \ > +} > + > +DEFINE_TEST_ARRAY_NAMED_TYPED(void, int, void, void *, int, void *) = { > + {NULL, 0, NULL, NULL, NULL, false, false, false}, > + {(void *)0x30, 0x10, (void *)0x40, NULL, NULL, false, false, false}, > + {(void *)ULONG_MAX, 0, (void *)ULONG_MAX, NULL, NULL, false, false, false}, > + {(void *)ULONG_MAX, 1, NULL, NULL, NULL, true, false, false}, > + {(void *)ULONG_MAX, INT_MAX, (void *)(INT_MAX - 1), NULL, NULL, true, false, false}, > +}; > +DEFINE_TEST_PTR_FUNC_TYPED(void_int__void, void *, "%lx"); > + > +struct _sized { > + int a; > + char b; > +}; > + > +DEFINE_TEST_ARRAY_NAMED_TYPED(sized, int, sized, struct _sized *, int, struct _sized *) = { > + {NULL, 0, NULL, NULL, NULL, false, false, false}, > + {NULL, 1, (struct _sized *)(sizeof(struct _sized)), NULL, NULL, false, false, false}, > + {NULL, 0x10, (struct _sized *)(sizeof(struct _sized) * 0x10), NULL, NULL, false, false, false}, > + {(void *)(ULONG_MAX - sizeof(struct _sized)), 1, (struct _sized *)ULONG_MAX, NULL, NULL, false, false, false}, > + {(void *)(ULONG_MAX - sizeof(struct _sized) + 1), 1, NULL, NULL, NULL, true, false, false}, > + {(void *)(ULONG_MAX - sizeof(struct _sized) + 1), 2, (struct _sized *)(sizeof(struct _sized)), NULL, NULL, true, false, false}, > + {(void *)(ULONG_MAX - sizeof(struct _sized) + 1), 3, (struct _sized *)(sizeof(struct _sized) * 2), NULL, NULL, true, false, false}, > +}; > +DEFINE_TEST_PTR_FUNC_TYPED(sized_int__sized, struct _sized *, "%lx"); > + > +DEFINE_TEST_ARRAY_NAMED_TYPED(sized, size_t, sized, struct _sized *, size_t, struct _sized *) = { > + {NULL, 0, NULL, NULL, NULL, false, false, false}, > + {NULL, 1, (struct _sized *)(sizeof(struct _sized)), NULL, NULL, false, false, false}, > + {NULL, 0x10, (struct _sized *)(sizeof(struct _sized) * 0x10), NULL, NULL, false, false, false}, > + {NULL, SIZE_MAX - 10, (struct _sized *)18446744073709551528UL, NULL, NULL, true, false, false}, > +}; > +DEFINE_TEST_PTR_FUNC_TYPED(sized_size_t__sized, struct _sized *, "%zu"); > + > /* Args are: value, shift, type, expected result, overflow expected */ > #define TEST_ONE_SHIFT(a, s, t, expect, of) do { \ > typeof(a) __a = (a); \ > @@ -1122,6 +1178,9 @@ static struct kunit_case overflow_test_cases[] = { > KUNIT_CASE(s32_s32__s32_overflow_test), > KUNIT_CASE(u64_u64__u64_overflow_test), > KUNIT_CASE(s64_s64__s64_overflow_test), > + KUNIT_CASE(void_int__void_overflow_test), > + KUNIT_CASE(sized_int__sized_overflow_test), > + KUNIT_CASE(sized_size_t__sized_overflow_test), > KUNIT_CASE(u32_u32__int_overflow_test), > KUNIT_CASE(u32_u32__u8_overflow_test), > KUNIT_CASE(u8_u8__int_overflow_test), > -- > 2.34.1 > Thanks Justin
On Fri, Jan 26, 2024 at 10:52:57PM +0000, Justin Stitt wrote: > [...] > > /** > > * check_sub_overflow() - Calculate subtraction with overflow checking > > Does check_sub_overflow() deserve some more love in the future? I > imagine "under"-flowing pointers is not at all common, though. Yes, though I hadn't found any cases of it yet in the code, so I didn't want to add a helper that would go unused. :) > Nonetheless, this all looks good to me. > > Reviewed-by: Justin Stitt <justinstitt@google.com> Thanks!
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h index 6f1ca49306d2..d27b58fddfaa 100644 --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -375,6 +375,16 @@ struct ftrace_likely_data { /* Are two types/vars the same type (ignoring qualifiers)? */ #define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b)) +/* Is variable addressable? */ +#define __is_ptr_or_array(p) (__builtin_classify_type(p) == 5) + +/* Return an array decayed to a pointer. */ +#define __decay(p) \ + (&*__builtin_choose_expr(__is_ptr_or_array(p), p, NULL)) + +/* Report if variable is a pointer type. */ +#define __is_ptr(p) __same_type(p, __decay(p)) + /* * __unqual_scalar_typeof(x) - Declare an unqualified scalar type, leaving * non-scalar types unchanged. diff --git a/include/linux/overflow.h b/include/linux/overflow.h index 7b5cf4a5cd19..099f2e559aa8 100644 --- a/include/linux/overflow.h +++ b/include/linux/overflow.h @@ -51,6 +51,45 @@ static inline bool __must_check __must_check_overflow(bool overflow) return unlikely(overflow); } +/* Always produce an integral variable expression. */ +#define __filter_integral(x) \ + __builtin_choose_expr(!__is_ptr(x), (x), 0) + +/* Always produce a pointer value. */ +#define __filter_ptr(x) \ + __builtin_choose_expr(__is_ptr(x), (x), NULL) + +/* Always produce a pointer to an integral value. */ +#define __filter_ptrint(x) \ + __builtin_choose_expr(!__is_ptr(*(x)), x, &(int){ 0 }) + +/** + * __check_ptr_add_overflow() - Calculate pointer addition with overflow checking + * @a: pointer addend + * @b: numeric addend + * @d: pointer to store sum + * + * Returns 0 on success. + * + * Do not use this function directly, use check_add_overflow() instead. + * + * *@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_ptr_add_overflow(a, b, d) \ + ({ \ + typeof(a) __a = (a); \ + typeof(b) __b = (b); \ + size_t __bytes; \ + bool __overflow; \ + \ + /* we want to perform the wrap-around, but retain the result */ \ + __overflow = __builtin_mul_overflow(sizeof(*(__a)), __b, &__bytes); \ + __builtin_add_overflow((unsigned long)(__a), __bytes, (unsigned long *)(d)) || \ + __overflow; \ + }) + /** * check_add_overflow() - Calculate addition with overflow checking * @a: first addend @@ -64,7 +103,10 @@ static inline bool __must_check __must_check_overflow(bool overflow) * sum has overflowed or been truncated. */ #define check_add_overflow(a, b, d) \ - __must_check_overflow(__builtin_add_overflow(a, b, d)) + __must_check_overflow(__builtin_choose_expr(__is_ptr(a), \ + __check_ptr_add_overflow(__filter_ptr(a), b, d), \ + __builtin_add_overflow(__filter_integral(a), b, \ + __filter_ptrint(d)))) /** * check_sub_overflow() - Calculate subtraction with overflow checking diff --git a/lib/overflow_kunit.c b/lib/overflow_kunit.c index c527f6b75789..2d106e880956 100644 --- a/lib/overflow_kunit.c +++ b/lib/overflow_kunit.c @@ -45,13 +45,18 @@ # define SKIP_64_ON_32(t) do { } while (0) #endif -#define DEFINE_TEST_ARRAY_TYPED(t1, t2, t) \ - static const struct test_ ## t1 ## _ ## t2 ## __ ## t { \ +#define DEFINE_TEST_ARRAY_NAMED_TYPED(n1, n2, n, t1, t2, t) \ + static const struct test_ ## n1 ## _ ## n2 ## __ ## n { \ t1 a; \ t2 b; \ - t sum, diff, prod; \ + t sum; \ + t diff; \ + t prod; \ bool s_of, d_of, p_of; \ - } t1 ## _ ## t2 ## __ ## t ## _tests[] + } n1 ## _ ## n2 ## __ ## n ## _tests[] + +#define DEFINE_TEST_ARRAY_TYPED(t1, t2, t) \ + DEFINE_TEST_ARRAY_NAMED_TYPED(t1, t2, t, t1, t2, t) #define DEFINE_TEST_ARRAY(t) DEFINE_TEST_ARRAY_TYPED(t, t, t) @@ -251,8 +256,10 @@ DEFINE_TEST_ARRAY(s64) = { }; #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; \ + typeof(a + 0) _a_orig = a; \ + typeof(a + 0) _a_bump = a + 1; \ + typeof(b + 0) _b_orig = b; \ + typeof(b + 0) _b_bump = b + 1; \ bool _of; \ t _r; \ \ @@ -260,13 +267,13 @@ DEFINE_TEST_ARRAY(s64) = { 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, \ + KUNIT_EXPECT_TRUE_MSG(test, _r == r, \ "expected "fmt" "sym" "fmt" == "fmt", got "fmt" (type %s)\n", \ 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"); \ + KUNIT_EXPECT_TRUE_MSG(test, _a_orig == _a_bump, "Unexpected " #op " macro side-effect!\n"); \ + KUNIT_EXPECT_TRUE_MSG(test, _b_orig == _b_bump, "Unexpected " #op " macro side-effect!\n"); \ } while (0) #define DEFINE_TEST_FUNC_TYPED(n, t, fmt) \ @@ -333,6 +340,55 @@ DEFINE_TEST_ARRAY_TYPED(int, int, u8) = { }; DEFINE_TEST_FUNC_TYPED(int_int__u8, u8, "%d"); +#define DEFINE_TEST_PTR_FUNC_TYPED(n, t, fmt) \ +static void do_ptr_test_ ## n(struct kunit *test, const struct test_ ## n *p) \ +{ \ + /* we're only doing single-direction sums, no product or division */ \ + check_one_op(t, fmt, add, "+", p->a, p->b, p->sum, p->s_of);\ +} \ + \ +static void n ## _overflow_test(struct kunit *test) { \ + unsigned i; \ + \ + for (i = 0; i < ARRAY_SIZE(n ## _tests); ++i) \ + do_ptr_test_ ## n(test, &n ## _tests[i]); \ + kunit_info(test, "%zu %s arithmetic tests finished\n", \ + ARRAY_SIZE(n ## _tests), #n); \ +} + +DEFINE_TEST_ARRAY_NAMED_TYPED(void, int, void, void *, int, void *) = { + {NULL, 0, NULL, NULL, NULL, false, false, false}, + {(void *)0x30, 0x10, (void *)0x40, NULL, NULL, false, false, false}, + {(void *)ULONG_MAX, 0, (void *)ULONG_MAX, NULL, NULL, false, false, false}, + {(void *)ULONG_MAX, 1, NULL, NULL, NULL, true, false, false}, + {(void *)ULONG_MAX, INT_MAX, (void *)(INT_MAX - 1), NULL, NULL, true, false, false}, +}; +DEFINE_TEST_PTR_FUNC_TYPED(void_int__void, void *, "%lx"); + +struct _sized { + int a; + char b; +}; + +DEFINE_TEST_ARRAY_NAMED_TYPED(sized, int, sized, struct _sized *, int, struct _sized *) = { + {NULL, 0, NULL, NULL, NULL, false, false, false}, + {NULL, 1, (struct _sized *)(sizeof(struct _sized)), NULL, NULL, false, false, false}, + {NULL, 0x10, (struct _sized *)(sizeof(struct _sized) * 0x10), NULL, NULL, false, false, false}, + {(void *)(ULONG_MAX - sizeof(struct _sized)), 1, (struct _sized *)ULONG_MAX, NULL, NULL, false, false, false}, + {(void *)(ULONG_MAX - sizeof(struct _sized) + 1), 1, NULL, NULL, NULL, true, false, false}, + {(void *)(ULONG_MAX - sizeof(struct _sized) + 1), 2, (struct _sized *)(sizeof(struct _sized)), NULL, NULL, true, false, false}, + {(void *)(ULONG_MAX - sizeof(struct _sized) + 1), 3, (struct _sized *)(sizeof(struct _sized) * 2), NULL, NULL, true, false, false}, +}; +DEFINE_TEST_PTR_FUNC_TYPED(sized_int__sized, struct _sized *, "%lx"); + +DEFINE_TEST_ARRAY_NAMED_TYPED(sized, size_t, sized, struct _sized *, size_t, struct _sized *) = { + {NULL, 0, NULL, NULL, NULL, false, false, false}, + {NULL, 1, (struct _sized *)(sizeof(struct _sized)), NULL, NULL, false, false, false}, + {NULL, 0x10, (struct _sized *)(sizeof(struct _sized) * 0x10), NULL, NULL, false, false, false}, + {NULL, SIZE_MAX - 10, (struct _sized *)18446744073709551528UL, NULL, NULL, true, false, false}, +}; +DEFINE_TEST_PTR_FUNC_TYPED(sized_size_t__sized, struct _sized *, "%zu"); + /* Args are: value, shift, type, expected result, overflow expected */ #define TEST_ONE_SHIFT(a, s, t, expect, of) do { \ typeof(a) __a = (a); \ @@ -1122,6 +1178,9 @@ static struct kunit_case overflow_test_cases[] = { KUNIT_CASE(s32_s32__s32_overflow_test), KUNIT_CASE(u64_u64__u64_overflow_test), KUNIT_CASE(s64_s64__s64_overflow_test), + KUNIT_CASE(void_int__void_overflow_test), + KUNIT_CASE(sized_int__sized_overflow_test), + KUNIT_CASE(sized_size_t__sized_overflow_test), KUNIT_CASE(u32_u32__int_overflow_test), KUNIT_CASE(u32_u32__u8_overflow_test), KUNIT_CASE(u8_u8__int_overflow_test),
The check_add_overflow() helper is mostly a wrapper around __builtin_add_overflow(), but GCC and Clang refuse to operate on pointer arguments that would normally be allowed if the addition were open-coded. For example, we have many places where pointer overflow is tested: struct foo *ptr; ... /* Check for overflow */ if (ptr + count < ptr) ... And in order to avoid running into the overflow sanitizers in the future, we need to rewrite these "intended" overflow checks: if (check_add_overflow(ptr, count, &result)) ... Frustratingly the argument type validation for __builtin_add_overflow() is done before evaluating __builtin_choose_expr(), so for arguments to be valid simultaneously for sizeof(*p) (when p may not be a pointer), and __builtin_add_overflow(a, ...) (when a may be a pointer), we must introduce wrappers that always produce a specific type (but they are only used in the places where the bogus arguments will be ignored). To test whether a variable is a pointer or not, introduce the __is_ptr() helper, which uses __builtin_classify_type() to find arrays and pointers (via the new __is_ptr_or_array() helper), and then decays arrays into pointers (via the new __decay() helper), to distinguish pointers from arrays. Additionally update the unit tests to cover pointer addition. Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Nathan Chancellor <nathan@kernel.org> Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Bill Wendling <morbo@google.com> Cc: Justin Stitt <justinstitt@google.com> Cc: llvm@lists.linux.dev Cc: linux-hardening@vger.kernel.org Signed-off-by: Kees Cook <keescook@chromium.org> --- include/linux/compiler_types.h | 10 +++++ include/linux/overflow.h | 44 ++++++++++++++++++- lib/overflow_kunit.c | 77 ++++++++++++++++++++++++++++++---- 3 files changed, 121 insertions(+), 10 deletions(-)