kunit/fortify: Fix memcmp() test to be amplitude agnostic

When memcmp() returns a non-zero value, only the signed bit has any
meaning. The actual value may differ between implementations.

Reported-by: Nathan Chancellor <nathan@kernel.org>
Closes: https://github.com/ClangBuiltLinux/linux/issues/2025
Tested-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20240518184020.work.604-kees@kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>

diff --git a/lib/fortify_kunit.c b/lib/fortify_kunit.c
index d2377e00caab43883a5e1516d029cc28109c1872..39da5b3bc649c28896e60d9dac974b98973da8d0 100644 (file)
--- a/lib/fortify_kunit.c
+++ b/lib/fortify_kunit.c
@@ -990,7 +990,7 @@ static void fortify_test_memcmp(struct kunit *test)
        KUNIT_ASSERT_EQ(test, memcmp(one, two, one_len), 0);
        KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
        /* Still in bounds, but no longer matching. */
-       KUNIT_ASSERT_EQ(test, memcmp(one, two, one_len + 1), -32);
+       KUNIT_ASSERT_LT(test, memcmp(one, two, one_len + 1), 0);
        KUNIT_EXPECT_EQ(test, fortify_read_overflows, 0);
 
        /* Catch too-large ranges. */