It seems that Clang thinks __builtin_constant_p() of undefined variables should return true[1]. This is being fixed separately[2], but in the meantime, expand the fortify tests to help track this kind of thing down faster in the future.
Link: https://github.com/ClangBuiltLinux/linux/issues/2073 [1] Link: https://github.com/llvm/llvm-project/pull/130713 [2] Signed-off-by: Kees Cook <k...@kernel.org> --- Cc: Nathan Chancellor <nat...@kernel.org> Cc: linux-hardening@vger.kernel.org --- lib/tests/fortify_kunit.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/lib/tests/fortify_kunit.c b/lib/tests/fortify_kunit.c index ecb638d4cde1..18dcdedf777f 100644 --- a/lib/tests/fortify_kunit.c +++ b/lib/tests/fortify_kunit.c @@ -60,6 +60,7 @@ static int fortify_write_overflows; static const char array_of_10[] = "this is 10"; static const char *ptr_of_11 = "this is 11!"; +static const char * const unchanging_12 = "this is 12!!"; static char array_unknown[] = "compiler thinks I might change"; void fortify_add_kunit_error(int write) @@ -83,12 +84,28 @@ void fortify_add_kunit_error(int write) static void fortify_test_known_sizes(struct kunit *test) { + char stack[80] = "Test!"; + + KUNIT_EXPECT_FALSE(test, __is_constexpr(__builtin_strlen(stack))); + KUNIT_EXPECT_EQ(test, __compiletime_strlen(stack), 5); + + KUNIT_EXPECT_TRUE(test, __is_constexpr(__builtin_strlen("88888888"))); KUNIT_EXPECT_EQ(test, __compiletime_strlen("88888888"), 8); + + KUNIT_EXPECT_TRUE(test, __is_constexpr(__builtin_strlen(array_of_10))); KUNIT_EXPECT_EQ(test, __compiletime_strlen(array_of_10), 10); + + KUNIT_EXPECT_FALSE(test, __is_constexpr(__builtin_strlen(ptr_of_11))); KUNIT_EXPECT_EQ(test, __compiletime_strlen(ptr_of_11), 11); + KUNIT_EXPECT_TRUE(test, __is_constexpr(__builtin_strlen(unchanging_12))); + KUNIT_EXPECT_EQ(test, __compiletime_strlen(unchanging_12), 12); + + KUNIT_EXPECT_FALSE(test, __is_constexpr(__builtin_strlen(array_unknown))); KUNIT_EXPECT_EQ(test, __compiletime_strlen(array_unknown), SIZE_MAX); + /* Externally defined and dynamically sized string pointer: */ + KUNIT_EXPECT_FALSE(test, __is_constexpr(__builtin_strlen(test->name))); KUNIT_EXPECT_EQ(test, __compiletime_strlen(test->name), SIZE_MAX); } -- 2.34.1
