Messages in this thread Patch in this message | | | From | Arnd Bergmann <> | Subject | [PATCH 1/2] kasan: test: use underlying string helpers | Date | Wed, 13 Oct 2021 17:00:05 +0200 |
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From: Arnd Bergmann <arnd@arndb.de>
Calling memcmp() and memchr() with an intentional buffer overflow is now caught at compile time:
In function 'memcmp', inlined from 'kasan_memcmp' at lib/test_kasan.c:897:2: include/linux/fortify-string.h:263:25: error: call to '__read_overflow' declared with attribute error: detected read beyond size of object (1st parameter) 263 | __read_overflow(); | ^~~~~~~~~~~~~~~~~ In function 'memchr', inlined from 'kasan_memchr' at lib/test_kasan.c:872:2: include/linux/fortify-string.h:277:17: error: call to '__read_overflow' declared with attribute error: detected read beyond size of object (1st parameter) 277 | __read_overflow(); | ^~~~~~~~~~~~~~~~~
Change the kasan tests to wrap those inside of a noinline function to prevent the compiler from noticing the bug and let kasan find it at runtime.
Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- lib/test_kasan.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-)
diff --git a/lib/test_kasan.c b/lib/test_kasan.c index 67ed689a0b1b..903215e944f1 100644 --- a/lib/test_kasan.c +++ b/lib/test_kasan.c @@ -852,6 +852,21 @@ static void kmem_cache_invalid_free(struct kunit *test) kmem_cache_destroy(cache); } +/* + * noinline wrappers to prevent the compiler from noticing the overflow + * at compile time rather than having kasan catch it. + * */ +static noinline void *__kasan_memchr(const void *s, int c, size_t n) +{ + return memchr(s, c, n); +} + +static noinline int __kasan_memcmp(const void *s1, const void *s2, size_t n) +{ + return memcmp(s1, s2, n); +} + + static void kasan_memchr(struct kunit *test) { char *ptr; @@ -870,7 +885,7 @@ static void kasan_memchr(struct kunit *test) KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr); KUNIT_EXPECT_KASAN_FAIL(test, - kasan_ptr_result = memchr(ptr, '1', size + 1)); + kasan_ptr_result = __kasan_memchr(ptr, '1', size + 1)); kfree(ptr); } @@ -895,7 +910,7 @@ static void kasan_memcmp(struct kunit *test) memset(arr, 0, sizeof(arr)); KUNIT_EXPECT_KASAN_FAIL(test, - kasan_int_result = memcmp(ptr, arr, size+1)); + kasan_int_result = __kasan_memcmp(ptr, arr, size+1)); kfree(ptr); } -- 2.29.2
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