ima: Set again build_ima_appraise variable

After adding the new add_rule() function in commit c52657d9
("ima: refactor ima_init_policy()"), all appraisal flags are added to the
temp_ima_appraise variable. Revert to the previous behavior instead of
removing build_ima_appraise, to benefit from the protection offered by
__ro_after_init.

The mentioned commit introduced a bug, as it makes all the flags
modifiable, while build_ima_appraise flags can be protected with
__ro_after_init.

Cc: stable@vger.kernel.org # 5.0.x
Fixes: c52657d9 ("ima: refactor ima_init_policy()")
Co-developed-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Krzysztof Struczynski <krzysztof.struczynski@huawei.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

security/integrity/ima/ima_policy.c

@@ -643,8 +643,14 @@ static void add_rules(struct ima_rule_entry *entries, int count,
 
 			list_add_tail(&entry->list, &ima_policy_rules);
 		}
-		if (entries[i].action == APPRAISE)
-			temp_ima_appraise |= ima_appraise_flag(entries[i].func);
+		if (entries[i].action == APPRAISE) {
+			if (entries != build_appraise_rules)
+				temp_ima_appraise |=
+					ima_appraise_flag(entries[i].func);
+			else
+				build_ima_appraise |=
+					ima_appraise_flag(entries[i].func);
+		}
 	}
 }