Bluetooth: don't release the port in rfcomm_dev_state_change()
When the dlc is closed, rfcomm_dev_state_change() tries to release the
port in the case it cannot get a reference to the tty. However this is
racy and not even needed.
Infact as Peter Hurley points out:
1. Only consider dlcs that are 'stolen' from a connected socket, ie.
reused. Allocated dlcs cannot have been closed prior to port
activate and so for these dlcs a tty reference will always be avail
in rfcomm_dev_state_change() -- except for the conditions covered by
#2b below.
2. If a tty was at some point previously created for this rfcomm, then
either
(a) the tty reference is still avail, so rfcomm_dev_state_change()
will perform a hangup. So nothing to do, or,
(b) the tty reference is no longer avail, and the tty_port will be
destroyed by the last tty_port_put() in rfcomm_tty_cleanup.
Again, no action required.
3. Prior to obtaining the dlc lock in rfcomm_dev_add(),
rfcomm_dev_state_change() will not 'see' a rfcomm_dev so nothing to
do here.
4. After releasing the dlc lock in rfcomm_dev_add(),
rfcomm_dev_state_change() will 'see' an incomplete rfcomm_dev if a
tty reference could not be obtained. Again, the best thing to do here
is nothing. Any future attempted open() will block on
rfcomm_dev_carrier_raised(). The unconnected device will exist until
released by ioctl(RFCOMMRELEASEDEV).
The patch removes the aforementioned code and uses the
tty_port_tty_hangup() helper to hangup the tty.
Signed-off-by: Gianluca Anzolin <gianluca@sottospazio.it>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
diff --git a/net/bluetooth/rfcomm/tty.c b/net/bluetooth/rfcomm/tty.c
index 6d126fa..84fcf9f 100644
--- a/net/bluetooth/rfcomm/tty.c
+++ b/net/bluetooth/rfcomm/tty.c
@@ -569,7 +569,6 @@
static void rfcomm_dev_state_change(struct rfcomm_dlc *dlc, int err)
{
struct rfcomm_dev *dev = dlc->owner;
- struct tty_struct *tty;
if (!dev)
return;
@@ -581,38 +580,8 @@
DPM_ORDER_DEV_AFTER_PARENT);
wake_up_interruptible(&dev->port.open_wait);
- } else if (dlc->state == BT_CLOSED) {
- tty = tty_port_tty_get(&dev->port);
- if (!tty) {
- if (test_bit(RFCOMM_RELEASE_ONHUP, &dev->flags)) {
- /* Drop DLC lock here to avoid deadlock
- * 1. rfcomm_dev_get will take rfcomm_dev_lock
- * but in rfcomm_dev_add there's lock order:
- * rfcomm_dev_lock -> dlc lock
- * 2. tty_port_put will deadlock if it's
- * the last reference
- *
- * FIXME: when we release the lock anything
- * could happen to dev, even its destruction
- */
- rfcomm_dlc_unlock(dlc);
- if (rfcomm_dev_get(dev->id) == NULL) {
- rfcomm_dlc_lock(dlc);
- return;
- }
-
- if (!test_and_set_bit(RFCOMM_TTY_RELEASED,
- &dev->flags))
- tty_port_put(&dev->port);
-
- tty_port_put(&dev->port);
- rfcomm_dlc_lock(dlc);
- }
- } else {
- tty_hangup(tty);
- tty_kref_put(tty);
- }
- }
+ } else if (dlc->state == BT_CLOSED)
+ tty_port_tty_hangup(&dev->port, false);
}
static void rfcomm_dev_modem_status(struct rfcomm_dlc *dlc, u8 v24_sig)