ima: ima/lsm policy rule loading logic bug fixes

mainline inclusion
from mainline-v5.6-rc1
commit 483ec26e
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I692HU
CVE: NA

--------------------------------

Keep the ima policy rules around from the beginning even if they appear
invalid at the time of loading, as they may become active after an lsm
policy load.  However, loading a custom IMA policy with unknown LSM
labels is only safe after we have transitioned from the "built-in"
policy rules to a custom IMA policy.

Patch also fixes the rule re-use during the lsm policy reload and makes
some prints a bit more human readable.

Changelog:
v4:
- Do not allow the initial policy load refer to non-existing lsm rules.
v3:
- Fix too wide policy rule matching for non-initialized LSMs
v2:
- Fix log prints

Fixes: b1694245 ("ima: use the lsm policy update notifier")
Cc: Casey Schaufler <casey@schaufler-ca.com>
Reported-by: NMimi Zohar <zohar@linux.ibm.com>
Signed-off-by: NJanne Karhunen <janne.karhunen@gmail.com>
Signed-off-by: NKonsta Karsisto <konsta.karsisto@gmail.com>
Signed-off-by: NMimi Zohar <zohar@linux.ibm.com>
Conflicts:
	security/integrity/ima/ima_policy.c
Signed-off-by: NGUO Zihua <guozihua@huawei.com>
Reviewed-by: NXiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: NYongqiang Liu <liuyongqiang13@huawei.com>

security/integrity/ima/ima_policy.c

@@ -264,7 +264,7 @@ static void ima_free_rule(struct ima_rule_entry *entry)
 static struct ima_rule_entry *ima_lsm_copy_rule(struct ima_rule_entry *entry)
 {
 	struct ima_rule_entry *nentry;
-	int i, result;
+	int i;
 
 	nentry = kmalloc(sizeof(*nentry), GFP_KERNEL);
 	if (!nentry)
@@ -278,7 +278,7 @@ static struct ima_rule_entry *ima_lsm_copy_rule(struct ima_rule_entry *entry)
 	memset(nentry->lsm, 0, FIELD_SIZEOF(struct ima_rule_entry, lsm));
 
 	for (i = 0; i < MAX_LSM_RULES; i++) {
-		if (!entry->lsm[i].rule)
+		if (!entry->lsm[i].args_p)
 			continue;
 
 		nentry->lsm[i].type = entry->lsm[i].type;
@@ -287,13 +287,13 @@ static struct ima_rule_entry *ima_lsm_copy_rule(struct ima_rule_entry *entry)
 		if (!nentry->lsm[i].args_p)
 			goto out_err;
 
-		result = security_filter_rule_init(nentry->lsm[i].type,
-						   Audit_equal,
-						   nentry->lsm[i].args_p,
-						   &nentry->lsm[i].rule);
-		if (result == -EINVAL)
-			pr_warn("ima: rule for LSM \'%d\' is undefined\n",
-				entry->lsm[i].type);
+		security_filter_rule_init(nentry->lsm[i].type,
+					  Audit_equal,
+					  nentry->lsm[i].args_p,
+					  &nentry->lsm[i].rule);
+		if (!nentry->lsm[i].rule)
+			pr_warn("rule for LSM \'%s\' is undefined\n",
+				(char *)entry->lsm[i].args_p);
 	}
 	return nentry;
 
@@ -332,7 +332,7 @@ static void ima_lsm_update_rules(void)
 	list_for_each_entry_safe(entry, e, &ima_policy_rules, list) {
 		needs_update = 0;
 		for (i = 0; i < MAX_LSM_RULES; i++) {
-			if (entry->lsm[i].rule) {
+			if (entry->lsm[i].args_p) {
 				needs_update = 1;
 				break;
 			}
@@ -342,8 +342,7 @@ static void ima_lsm_update_rules(void)
 
 		result = ima_lsm_update_rule(entry);
 		if (result) {
-			pr_err("ima: lsm rule update error %d\n",
-				result);
+			pr_err("lsm rule update error %d\n", result);
 			return;
 		}
 	}
@@ -360,7 +359,7 @@ int ima_lsm_policy_change(struct notifier_block *nb, unsigned long event,
 }
 
 /**
- * ima_match_rules - determine whether an inode matches the measure rule.
+ * ima_match_rules - determine whether an inode matches the policy rule.
  * @rule: a pointer to a rule
  * @inode: a pointer to an inode
  * @cred: a pointer to a credentials structure for user validation
@@ -416,8 +415,12 @@ static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode,
 		int rc = 0;
 		u32 osid;
 
-		if (!lsm_rule->lsm[i].rule)
-			continue;
+		if (!lsm_rule->lsm[i].rule) {
+			if (!lsm_rule->lsm[i].args_p)
+				continue;
+			else
+				return false;
+		}
 
 retry:
 		switch (i) {
@@ -755,9 +758,15 @@ static int ima_lsm_rule_init(struct ima_rule_entry *entry,
 					   entry->lsm[lsm_rule].args_p,
 					   &entry->lsm[lsm_rule].rule);
 	if (!entry->lsm[lsm_rule].rule) {
-		kfree(entry->lsm[lsm_rule].args_p);
-		entry->lsm[lsm_rule].args_p = NULL;
-		return -EINVAL;
+		pr_warn("rule for LSM \'%s\' is undefined\n",
+			(char *)entry->lsm[lsm_rule].args_p);
+
+		if (ima_rules == &ima_default_rules) {
+			kfree(entry->lsm[lsm_rule].args_p);
+			entry->lsm[lsm_rule].args_p = NULL;
+			result = -EINVAL;
+		} else
+			result = 0;
 	}
 
 	return result;