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

From: Tyler Hicks
Date: Mon Jun 22 2020 - 20:34:21 EST


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 <tyhicks@xxxxxxxxxxxxxxxxxxx>
---
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