linux-kernel - [RFC PATCH] security/apparmor: use kfree_sensitive() in unpack

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Message-Id: <20250418045250.1262935-1-zilin@seu.edu.cn>
Date: Fri, 18 Apr 2025 04:52:50 +0000
From: Zilin Guan <zilin@....edu.cn>
To: john.johansen@...onical.com
Cc: paul@...l-moore.com,
	jmorris@...ei.org,
	serge@...lyn.com,
	apparmor@...ts.ubuntu.com,
	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	jianhao.xu@....edu.cn,
	Zilin Guan <zilin@....edu.cn>
Subject: [RFC PATCH] security/apparmor: use kfree_sensitive() in unpack_secmark()

The unpack_secmark() function currently uses kfree() to release memory
allocated for secmark structures and their labels. However, if a failure
occurs after partially parsing secmark, sensitive data may remain in
memory, posing a security risk.

To mitigate this, replace kfree() with kfree_sensitive() for freeing
secmark structures and their labels, aligning with the approach used
in free_ruleset().

I am submitting this as an RFC to seek freedback on whether this change
is appropriate and aligns with the subsystem's expectations. If
confirmed to be helpful, I will send a formal patch.

Signed-off-by: Zilin Guan <zilin@....edu.cn>
---
 security/apparmor/policy_unpack.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/security/apparmor/policy_unpack.c b/security/apparmor/policy_unpack.c
index 992b74c50..610e09c76 100644
--- a/security/apparmor/policy_unpack.c
+++ b/security/apparmor/policy_unpack.c
@@ -598,8 +598,8 @@ static bool unpack_secmark(struct aa_ext *e, struct aa_ruleset *rules)
 fail:
 	if (rules->secmark) {
 		for (i = 0; i < size; i++)
-			kfree(rules->secmark[i].label);
-		kfree(rules->secmark);
+			kfree_sensitive(rules->secmark[i].label);
+		kfree_sensitive(rules->secmark);
 		rules->secmark_count = 0;
 		rules->secmark = NULL;
 	}
-- 
2.34.1