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Bluetooth: Fix RFCOMM tty teardown race 

RFCOMM tty device teardown can race with new tty device registration
for the same device id:

CPU 0                           | CPU 1
rfcomm_dev_add                  | rfcomm_dev_destruct
                                |   spin_lock
                                |   list_del   <== dev_id no longer used
                                |   spin_unlock
  spin_lock                     |     .
  [search rfcomm_dev_list]      |     .
  [dev_id not in use]           |     .
  [initialize new rfcomm_dev]   |     .
  spin_unlock                   |     .
                                |     .
  tty_port_register_device      |   tty_unregister_device

Don't remove rfcomm_dev from the device list until after tty device
unregistration has completed.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Tested-By: Alexander Holler <holler@ahsoftware.de>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
This commit is contained in:
Peter Hurley 2014-02-09 20:59:09 -05:00 committed by Marcel Holtmann
parent 80ea73378a
commit c949c224cf
1 changed files with 4 additions and 4 deletions
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8
net/bluetooth/rfcomm/tty.c
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@ -84,10 +84,6 @@ static void rfcomm_dev_destruct(struct tty_port *port)
BT_DBG("dev %p dlc %p", dev, dlc);
spin_lock(&rfcomm_dev_lock);
list_del(&dev->list);
spin_unlock(&rfcomm_dev_lock);
rfcomm_dlc_lock(dlc);
/* Detach DLC if it's owned by this dev */
if (dlc->owner == dev)
@ -98,6 +94,10 @@ static void rfcomm_dev_destruct(struct tty_port *port)
tty_unregister_device(rfcomm_tty_driver, dev->id);
spin_lock(&rfcomm_dev_lock);
list_del(&dev->list);
spin_unlock(&rfcomm_dev_lock);
kfree(dev);
/* It's safe to call module_put() here because socket still