2 files changed, 96 insertions, 0 deletions

diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h
index 7b4cc5b98535..fb94cf13c777 100644
--- a/include/net/bluetooth/l2cap.h
+++ b/include/net/bluetooth/l2cap.h
@@ -584,6 +584,13 @@ struct l2cap_conn {
         struct list_head        chan_l;
         struct mutex            chan_lock;
         struct kref             ref;
+        struct list_head        users;
+};
+
+struct l2cap_user {
+        struct list_head list;
+        int (*probe) (struct l2cap_conn *conn, struct l2cap_user *user);
+        void (*remove) (struct l2cap_conn *conn, struct l2cap_user *user);
 };
 
 #define L2CAP_INFO_CL_MTU_REQ_SENT      0x01
@@ -817,4 +824,7 @@ void __l2cap_physical_cfm(struct l2cap_chan *chan, int result);
 void l2cap_conn_get(struct l2cap_conn *conn);
 void l2cap_conn_put(struct l2cap_conn *conn);
 
+int l2cap_register_user(struct l2cap_conn *conn, struct l2cap_user *user);
+void l2cap_unregister_user(struct l2cap_conn *conn, struct l2cap_user *user);
+
 #endif /* __L2CAP_H */
diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index be9ad89339cd..eae1d9f90b68 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -1446,6 +1446,89 @@ static void l2cap_info_timeout(struct work_struct *work)
         l2cap_conn_start(conn);
 }
 
+/*
+ * l2cap_user
+ * External modules can register l2cap_user objects on l2cap_conn. The ->probe
+ * callback is called during registration. The ->remove callback is called
+ * during unregistration.
+ * An l2cap_user object can either be explicitly unregistered or when the
+ * underlying l2cap_conn object is deleted. This guarantees that l2cap->hcon,
+ * l2cap->hchan, .. are valid as long as the remove callback hasn't been called.
+ * External modules must own a reference to the l2cap_conn object if they intend
+ * to call l2cap_unregister_user(). The l2cap_conn object might get destroyed at
+ * any time if they don't.
+ */
+
+int l2cap_register_user(struct l2cap_conn *conn, struct l2cap_user *user)
+{
+        struct hci_dev *hdev = conn->hcon->hdev;
+        int ret;
+
+        /* We need to check whether l2cap_conn is registered. If it is not, we
+         * must not register the l2cap_user. l2cap_conn_del() is unregisters
+         * l2cap_conn objects, but doesn't provide its own locking. Instead, it
+         * relies on the parent hci_conn object to be locked. This itself relies
+         * on the hci_dev object to be locked. So we must lock the hci device
+         * here, too. */
+
+        hci_dev_lock(hdev);
+
+        if (user->list.next || user->list.prev) {
+                ret = -EINVAL;
+                goto out_unlock;
+        }
+
+        /* conn->hchan is NULL after l2cap_conn_del() was called */
+        if (!conn->hchan) {
+                ret = -ENODEV;
+                goto out_unlock;
+        }
+
+        ret = user->probe(conn, user);
+        if (ret)
+                goto out_unlock;
+
+        list_add(&user->list, &conn->users);
+        ret = 0;
+
+out_unlock:
+        hci_dev_unlock(hdev);
+        return ret;
+}
+EXPORT_SYMBOL(l2cap_register_user);
+
+void l2cap_unregister_user(struct l2cap_conn *conn, struct l2cap_user *user)
+{
+        struct hci_dev *hdev = conn->hcon->hdev;
+
+        hci_dev_lock(hdev);
+
+        if (!user->list.next || !user->list.prev)
+                goto out_unlock;
+
+        list_del(&user->list);
+        user->list.next = NULL;
+        user->list.prev = NULL;
+        user->remove(conn, user);
+
+out_unlock:
+        hci_dev_unlock(hdev);
+}
+EXPORT_SYMBOL(l2cap_unregister_user);
+
+static void l2cap_unregister_all_users(struct l2cap_conn *conn)
+{
+        struct l2cap_user *user;
+
+        while (!list_empty(&conn->users)) {
+                user = list_first_entry(&conn->users, struct l2cap_user, list);
+                list_del(&user->list);
+                user->list.next = NULL;
+                user->list.prev = NULL;
+                user->remove(conn, user);
+        }
+}
+
 static void l2cap_conn_del(struct hci_conn *hcon, int err)
 {
         struct l2cap_conn *conn = hcon->l2cap_data;
@@ -1458,6 +1541,8 @@ static void l2cap_conn_del(struct hci_conn *hcon, int err)
 
         kfree_skb(conn->rx_skb);
 
+        l2cap_unregister_all_users(conn);
+
         mutex_lock(&conn->chan_lock);
 
         /* Kill channels */
@@ -1550,6 +1635,7 @@ static struct l2cap_conn *l2cap_conn_add(struct hci_conn *hcon)
         mutex_init(&conn->chan_lock);
 
         INIT_LIST_HEAD(&conn->chan_l);
+        INIT_LIST_HEAD(&conn->users);
 
         if (hcon->type == LE_LINK)
                 INIT_DELAYED_WORK(&conn->security_timer, security_timeout);