[PATCH 02/12] ima: Create a function to free a rule entry

[Tyler Hicks]

There are several possible pieces of allocated memory in a rule entry.
Create a function that can free all allocated memory for a given rule
entry.

This patch introduces no functional changes but sets the groundwork for
some memory leak fixes.

Signed-off-by: Tyler Hicks <tyhi...@linux.microsoft.com>
---
 security/integrity/ima/ima_policy.c | 33 +++++++++++++++++++++++++++--
 1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/security/integrity/ima/ima_policy.c 
b/security/integrity/ima/ima_policy.c
index 236a731492d1..1320333201c6 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -261,6 +261,27 @@ static void ima_lsm_free_rule(struct ima_rule_entry *entry)
                security_filter_rule_free(entry->lsm[i].rule);
                kfree(entry->lsm[i].args_p);
        }
+}
+
+static void ima_free_rule(struct ima_rule_entry *entry)
+{
+       if (!entry)
+               return;
+
+       /*
+        * entry->template->fields may be allocated in ima_parse_rule() but that
+        * reference is owned by the corresponding ima_template_desc element in
+        * the defined_templates list and cannot be freed here
+        */
+
+       /*
+        * When freeing newly added ima_rule_entry members, consider if you
+        * need to disown any references after the shallow copy in
+        * ima_lsm_copy_rule()
+        */
+       kfree(entry->fsname);
+       kfree(entry->keyrings);
+       ima_lsm_free_rule(entry);
        kfree(entry);
 }
 
@@ -298,10 +319,18 @@ static struct ima_rule_entry *ima_lsm_copy_rule(struct 
ima_rule_entry *entry)
                        pr_warn("rule for LSM \'%s\' is undefined\n",
                                (char *)entry->lsm[i].args_p);
        }
+
+       /* Disown all references that were shallow copied */
+       entry->fsname = NULL;
+       entry->keyrings = NULL;
+       entry->template = NULL;
        return nentry;
 
 out_err:
-       ima_lsm_free_rule(nentry);
+       nentry->fsname = NULL;
+       nentry->keyrings = NULL;
+       nentry->template = NULL;
+       ima_free_rule(nentry);
        return NULL;
 }
 
@@ -315,7 +344,7 @@ static int ima_lsm_update_rule(struct ima_rule_entry *entry)
 
        list_replace_rcu(&entry->list, &nentry->list);
        synchronize_rcu();
-       ima_lsm_free_rule(entry);
+       ima_free_rule(entry);
 
        return 0;
 }
-- 
2.25.1