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Commit b92483d5 authored by Peter Hurley's avatar Peter Hurley Committed by Marcel Holtmann
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Bluetooth: Fix unsafe RFCOMM device parenting 



Accessing the results of hci_conn_hash_lookup_ba() is unsafe without
holding the hci_dev_lock() during the lookup. For example:

CPU 0                             | CPU 1
hci_conn_hash_lookup_ba           | hci_conn_del
  rcu_read_lock                   |   hci_conn_hash_del
  list_for_each_entry_rcu         |     list_del_rcu
    if (.....)                    |       synchronize_rcu
      rcu_read_unlock             |
                                  |   hci_conn_del_sysfs
                                  |   hci_dev_put
                                  |   hci_conn_put
                                  |     put_device (last reference)
                                  |       bt_link_release
                                  |         kfree(conn)
      return p  << just freed     |

Even if a hci_conn reference were taken (via hci_conn_get), would
not guarantee the lifetime of the sysfs device, but only safe
access to the in-memory structure.

Ensure the hci_conn device stays valid while the rfcomm device
is reparented; rename rfcomm_get_device() to rfcomm_reparent_device()
and perform the reparenting within the function while holding the
hci_dev_lock.

Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Tested-By: default avatarAlexander Holler <holler@ahsoftware.de>
Signed-off-by: default avatarMarcel Holtmann <marcel@holtmann.org>
parent c4fd318d

net/bluetooth/rfcomm/tty.c

+14 −6
Original line number Diff line number Diff line
@@ -167,20 +167,29 @@ static struct rfcomm_dev *rfcomm_dev_get(int id) 
	return dev;

}



static struct device *rfcomm_get_device(struct rfcomm_dev *dev)

static void rfcomm_reparent_device(struct rfcomm_dev *dev)

{

	struct hci_dev *hdev;

	struct hci_conn *conn;



	hdev = hci_get_route(&dev->dst, &dev->src);

	if (!hdev)

		return NULL;

		return;



	/* The lookup results are unsafe to access without the

	 * hci device lock (FIXME: why is this not documented?)

	 */

	hci_dev_lock(hdev);

	conn = hci_conn_hash_lookup_ba(hdev, ACL_LINK, &dev->dst);



	hci_dev_put(hdev);

	/* Just because the acl link is in the hash table is no

	 * guarantee the sysfs device has been added ...

	 */

	if (conn && device_is_registered(&conn->dev))

		device_move(dev->tty_dev, &conn->dev, DPM_ORDER_DEV_AFTER_PARENT);



	return conn ? &conn->dev : NULL;

	hci_dev_unlock(hdev);

	hci_dev_put(hdev);

}



static ssize_t show_address(struct device *tty_dev, struct device_attribute *attr, char *buf)
@@ -589,8 +598,7 @@ static void rfcomm_dev_state_change(struct rfcomm_dlc *dlc, int err) 


	dev->err = err;

	if (dlc->state == BT_CONNECTED) {

		device_move(dev->tty_dev, rfcomm_get_device(dev),

			    DPM_ORDER_DEV_AFTER_PARENT);

		rfcomm_reparent_device(dev);



		wake_up_interruptible(&dev->port.open_wait);

	} else if (dlc->state == BT_CLOSED)