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>

diff --git a/net/bluetooth/rfcomm/tty.c b/net/bluetooth/rfcomm/tty.c
index bb570d95adca2d589cf9f1560b2cfa5685f3d9c0..6ea08b05b53a0ed19db047cc69c780aca7c05389 100644 (file)
--- a/net/bluetooth/rfcomm/tty.c
+++ b/net/bluetooth/rfcomm/tty.c
@@ -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