audit: enforce AUDIT_LOCKED for AUDIT_TRIM and AUDIT_MAKE_EQUIV

AUDIT_ADD_RULE and AUDIT_DEL_RULE correctly check for AUDIT_LOCKED
and return -EPERM, but AUDIT_TRIM and AUDIT_MAKE_EQUIV do not. This
allows a process with CAP_AUDIT_CONTROL to modify directory tree
watches and equivalence mappings even when the audit configuration
has been locked, undermining the purpose of the lock.

Add AUDIT_LOCKED checks to both commands.

Cc: stable@vger.kernel.org
Reviewed-by: Ricardo Robaina <rrobaina@redhat.com>
Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Sergio Correia <scorreia@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

kernel/audit.c

diff --git a/kernel/audit.c b/kernel/audit.c
index e1d489b..34dc7cb 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -1468,6 +1468,8 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
 		err = audit_list_rules_send(skb, seq);
 		break;
 	case AUDIT_TRIM:
+		if (audit_enabled == AUDIT_LOCKED)
+			return -EPERM;
 		audit_trim_trees();
 		audit_log_common_recv_msg(audit_context(), &ab,
 					  AUDIT_CONFIG_CHANGE);
@@ -1480,6 +1482,8 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
 		size_t msglen = data_len;
 		char *old, *new;
 
+		if (audit_enabled == AUDIT_LOCKED)
+			return -EPERM;
 		err = -EINVAL;
 		if (msglen < 2 * sizeof(u32))
 			break;