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

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Date:   Mon, 22 Jun 2020 19:32:26 -0500
From:   Tyler Hicks <tyhicks@...ux.microsoft.com>
To:     Mimi Zohar <zohar@...ux.ibm.com>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>
Cc:     James Morris <jmorris@...ei.org>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>,
        Prakhar Srivastava <prsriva02@...il.com>,
        linux-kernel@...r.kernel.org, linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org
Subject: [PATCH 02/12] ima: Create a function to free a rule entry

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@...ux.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