ima: Do not print policy rule with inactive LSM labels

Before printing a policy rule scan for inactive LSM labels in the policy
rule. Inactive LSM labels are identified by args_p != NULL and
rule == NULL.

Fixes: 483ec26 ("ima: ima/lsm policy rule loading logic bug fixes")
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Cc: <stable@vger.kernel.org> # v5.6+
Acked-by: Christian Brauner <brauner@kernel.org>
[zohar@linux.ibm.com: Updated "Fixes" tag]
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

Author: stefanberger

security/integrity/ima/ima_policy.c

@@ -1967,6 +1967,14 @@ int ima_policy_show(struct seq_file *m, void *v)
 
 	rcu_read_lock();
 
+	/* Do not print rules with inactive LSM labels */
+	for (i = 0; i < MAX_LSM_RULES; i++) {
+		if (entry->lsm[i].args_p && !entry->lsm[i].rule) {
+			rcu_read_unlock();
+			return 0;
+		}
+	}
+
 	if (entry->action & MEASURE)
 		seq_puts(m, pt(Opt_measure));
 	if (entry->action & DONT_MEASURE)