ima: differentiate between EVM failures in the audit log

Differentiate between an invalid EVM portable signature failure
from other EVM HMAC/signature failures.
Reviewed-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

security/integrity/ima/ima_appraise.c

@@ -422,7 +422,8 @@ int ima_appraise_measurement(enum ima_hooks func,
 		goto out;
 	case INTEGRITY_FAIL_IMMUTABLE:
 		set_bit(IMA_DIGSIG, &iint->atomic_flags);
-		fallthrough;
+		cause = "invalid-fail-immutable";
+		goto out;
 	case INTEGRITY_FAIL:		/* Invalid HMAC/signature. */
 		cause = "invalid-HMAC";
 		goto out;