In the Linux kernel, the following vulnerability has been resolved: Bluetooth: ISO: fix...

In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: ISO: fix refcounting of iso_conn

iso_conn_del() and iso_chan_del() have a race that results to double-put of iso_conn:

[Task hdev->workqueue]         [Task 2]
iso_conn_del                   iso_chan_del
  iso_conn_hold_unless_zero      iso_conn_lock
  iso_conn_lock                  conn->sk = NULL
                                 iso_conn_unlock
  sk = iso_sock_hold(conn)  <---------´
  if (!sk) iso_conn_put          iso_conn_put
  iso_conn_put /* UAF */

The extra put for !sk in iso_conn_del() is currently required since failing iso_chan_add() may leave iso_conn not associated with any sk.

Fix by having iso_pi(sk)->conn own refcount when non-NULL, so iso_conn_del does not need to put it. Adjust the iso_conn_add() refcounting so that conn is put if it does not get associated with an sk.