[PATCH 2/2] Bluetooth: ISO: release unused CIS holds after channel attach

[Aldo Ariel Panzardo]

hci_bind_cis() and hci_connect_cis() return one hci_conn hold for the
ISO layer.  A new channel association consumes that hold, which is
eventually released by iso_conn_free().

There are two cases where iso_chan_add() does not create an association:
it returns success when the socket is already attached to the same
iso_conn, and it returns -EBUSY when another socket is attached.  The
hold returned for the current call is unused in both cases.  This occurs
when deferred setup calls iso_connect_cis() again for its existing
socket, or when another socket attempts to reuse the CIS.

Detect the idempotent case while the connection is locked and release
the unused hold after iso_chan_add().  Also release it on -EBUSY.  Do not
drop it for other errors: a newly allocated iso_conn releases the
transferred hold when its last temporary reference is put.

Fixes: 69997d50ec57 ("Bluetooth: ISO: handle bound CIS cleanup via hci_conn")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Aldo Ariel Panzardo <qwe.aldo@xxxxxxxxx>
---
 net/bluetooth/iso.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/net/bluetooth/iso.c b/net/bluetooth/iso.c
index a461c8a4ef..329bee9c2e 100644
--- a/net/bluetooth/iso.c
+++ b/net/bluetooth/iso.c
@@ -496,6 +496,7 @@ static int iso_connect_cis(struct sock *sk)
 	struct hci_dev  *hdev;
 	bdaddr_t src, dst;
 	u8 src_type;
+	bool already_attached;
 	int err;
 
 	lock_sock(sk);
@@ -568,8 +569,14 @@ static int iso_connect_cis(struct sock *sk)
 		goto unlock;
 	}
 
+	iso_conn_lock(conn);
+	already_attached = iso_pi(sk)->conn == conn && conn->sk == sk;
+	iso_conn_unlock(conn);
+
 	err = iso_chan_add(conn, sk, NULL);
 	iso_conn_put(conn);
+	if (already_attached || err == -EBUSY)
+		hci_conn_drop(hcon);
 	if (err)
 		goto unlock;
 
-- 
2.43.0