1 files changed, 99 insertions, 0 deletions
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index 3dba81c2eba..8ec02746ca9 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -1000,3 +1000,102 @@ static void keyring_revoke(struct key *keyring)
 	}
 
 } /* end keyring_revoke() */
+
+/*
+ * Determine whether a key is dead
+ */
+static bool key_is_dead(struct key *key, time_t limit)
+{
+	return test_bit(KEY_FLAG_DEAD, &key->flags) ||
+		(key->expiry > 0 && key->expiry <= limit);
+}
+
+/*
+ * Collect garbage from the contents of a keyring
+ */
+void keyring_gc(struct key *keyring, time_t limit)
+{
+	struct keyring_list *klist, *new;
+	struct key *key;
+	int loop, keep, max;
+
+	kenter("{%x,%s}", key_serial(keyring), keyring->description);
+
+	down_write(&keyring->sem);
+
+	klist = keyring->payload.subscriptions;
+	if (!klist)
+		goto no_klist;
+
+	/* work out how many subscriptions we're keeping */
+	keep = 0;
+	for (loop = klist->nkeys - 1; loop >= 0; loop--)
+		if (!key_is_dead(klist->keys[loop], limit))
+			keep++;
+
+	if (keep == klist->nkeys)
+		goto just_return;
+
+	/* allocate a new keyring payload */
+	max = roundup(keep, 4);
+	new = kmalloc(sizeof(struct keyring_list) + max * sizeof(struct key *),
+		      GFP_KERNEL);
+	if (!new)
+		goto nomem;
+	new->maxkeys = max;
+	new->nkeys = 0;
+	new->delkey = 0;
+
+	/* install the live keys
+	 * - must take care as expired keys may be updated back to life
+	 */
+	keep = 0;
+	for (loop = klist->nkeys - 1; loop >= 0; loop--) {
+		key = klist->keys[loop];
+		if (!key_is_dead(key, limit)) {
+			if (keep >= max)
+				goto discard_new;
+			new->keys[keep++] = key_get(key);
+		}
+	}
+	new->nkeys = keep;
+
+	/* adjust the quota */
+	key_payload_reserve(keyring,
+			    sizeof(struct keyring_list) +
+			    KEYQUOTA_LINK_BYTES * keep);
+
+	if (keep == 0) {
+		rcu_assign_pointer(keyring->payload.subscriptions, NULL);
+		kfree(new);
+	} else {
+		rcu_assign_pointer(keyring->payload.subscriptions, new);
+	}
+
+	up_write(&keyring->sem);
+
+	call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
+	kleave(" [yes]");
+	return;
+
+discard_new:
+	new->nkeys = keep;
+	keyring_clear_rcu_disposal(&new->rcu);
+	up_write(&keyring->sem);
+	kleave(" [discard]");
+	return;
+
+just_return:
+	up_write(&keyring->sem);
+	kleave(" [no dead]");
+	return;
+
+no_klist:
+	up_write(&keyring->sem);
+	kleave(" [no_klist]");
+	return;
+
+nomem:
+	up_write(&keyring->sem);
+	kleave(" [oom]");
+}