[PATCH 4.4 008/168] Bluetooth: Fix decrementing reference count twice in releasing socket

From: Greg Kroah-Hartman
Date: Wed Apr 24 2019 - 13:17:52 EST

From: Myungho Jung <mhjungk@xxxxxxxxx>

commit e20a2e9c42c9e4002d9e338d74e7819e88d77162 upstream.

When releasing socket, it is possible to enter hci_sock_release() and
hci_sock_dev_event(HCI_DEV_UNREG) at the same time in different thread.
The reference count of hdev should be decremented only once from one of
them but if storing hdev to local variable in hci_sock_release() before
detached from socket and setting to NULL in hci_sock_dev_event(),
hci_dev_put(hdev) is unexpectedly called twice. This is resolved by
referencing hdev from socket after bt_sock_unlink() in

Reported-by: syzbot+fdc00003f4efff43bc5b@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Myungho Jung <mhjungk@xxxxxxxxx>
Signed-off-by: Marcel Holtmann <marcel@xxxxxxxxxxxx>
Signed-off-by: Zubin Mithra <zsm@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

net/bluetooth/hci_sock.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

--- a/net/bluetooth/hci_sock.c
+++ b/net/bluetooth/hci_sock.c
@@ -558,13 +558,12 @@ static int hci_sock_release(struct socke
if (!sk)
return 0;

- hdev = hci_pi(sk)->hdev;
if (hci_pi(sk)->channel == HCI_CHANNEL_MONITOR)

bt_sock_unlink(&hci_sk_list, sk);

+ hdev = hci_pi(sk)->hdev;
if (hdev) {
if (hci_pi(sk)->channel == HCI_CHANNEL_USER) {
/* When releasing an user channel exclusive access,