[PATCH v2] ima: ima/lsm policy rule loading logic bug fixes

[Janne Karhunen <janne.karhunen@xxxxxxxxx>]

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 the lsm
policy load. In other words, now the lsm and the ima can be initialized
in any order and the handling logic is the same as with the lsm rule
reload event. With these changes, there is no need to defer loading a
custom IMA policy, based on LSM rules, until after the LSM policy has
been initialized.

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

Fixes: b16942455193 ("ima: use the lsm policy update notifier")
Cc: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
Reported-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
Reviewed-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
Signed-off-by: Janne Karhunen <janne.karhunen@xxxxxxxxx>
Signed-off-by: Konsta Karsisto <konsta.karsisto@xxxxxxxxx>
---
 security/integrity/ima/ima_policy.c | 44 ++++++++++++++---------------
 1 file changed, 21 insertions(+), 23 deletions(-)

diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index a4dde9d575b2..4022c7736fc3 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -265,7 +265,7 @@ static void ima_lsm_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)
@@ -279,7 +279,7 @@ 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;
@@ -288,13 +288,13 @@ 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;
 
@@ -331,7 +331,9 @@ 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) {
+				pr_info("rule for LSM \'%s\' needs update\n",
+					(char *)entry->lsm[i].args_p);
 				needs_update = 1;
 				break;
 			}
@@ -341,8 +343,7 @@ 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;
 		}
 	}
@@ -865,8 +866,6 @@ static const match_table_t policy_tokens = {
 static int ima_lsm_rule_init(struct ima_rule_entry *entry,
 			     substring_t *args, int lsm_rule, int audit_type)
 {
-	int result;
-
 	if (entry->lsm[lsm_rule].rule)
 		return -EINVAL;
 
@@ -875,16 +874,15 @@ static int ima_lsm_rule_init(struct ima_rule_entry *entry,
 		return -ENOMEM;
 
 	entry->lsm[lsm_rule].type = audit_type;
-	result = security_filter_rule_init(entry->lsm[lsm_rule].type,
-					   Audit_equal,
-					   entry->lsm[lsm_rule].args_p,
-					   &entry->lsm[lsm_rule].rule);
-	if (!entry->lsm[lsm_rule].rule) {
-		kfree(entry->lsm[lsm_rule].args_p);
-		return -EINVAL;
-	}
+	security_filter_rule_init(entry->lsm[lsm_rule].type,
+				  Audit_equal,
+				  entry->lsm[lsm_rule].args_p,
+				  &entry->lsm[lsm_rule].rule);
+	if (!entry->lsm[lsm_rule].rule)
+		pr_warn("rule for LSM \'%s\' is undefined\n",
+			(char *)entry->lsm[lsm_rule].args_p);
 
-	return result;
+	return 0;
 }
 
 static void ima_log_string_op(struct audit_buffer *ab, char *key, char *value,
-- 
2.17.1