Bluetooth: Release RFCOMM port when the last user closes the TTY

This patch fixes a userspace regression introduced by the commit
29cd718b.

If the rfcomm device was created with the flag RFCOMM_RELEASE_ONHUP the
user space expects that the tty_port is released as soon as the last
process closes the tty.

The current code attempts to release the port in the function
rfcomm_dev_state_change(). However it won't get a reference to the
relevant tty to send a HUP: at that point the tty is already destroyed
and therefore NULL.

This patch fixes the regression by taking over the tty refcount in the
tty install method(). This way the tty_port is automatically released as
soon as the tty is destroyed.

As a consequence the check for RFCOMM_RELEASE_ONHUP flag in the hangup()
method is now redundant. Instead we have to be careful with the reference
counting in the rfcomm_release_dev() function.

Signed-off-by: Gianluca Anzolin <gianluca@sottospazio.it>
Reported-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 84fcf9f..a535ef1 100644 (file)
--- a/net/bluetooth/rfcomm/tty.c
+++ b/net/bluetooth/rfcomm/tty.c
@@ -437,7 +437,8 @@ static int rfcomm_release_dev(void __user *arg)
                tty_kref_put(tty);
        }
 
-       if (!test_and_set_bit(RFCOMM_TTY_RELEASED, &dev->flags))
+       if (!test_bit(RFCOMM_RELEASE_ONHUP, &dev->flags) &&
+           !test_and_set_bit(RFCOMM_TTY_RELEASED, &dev->flags))
                tty_port_put(&dev->port);
 
        tty_port_put(&dev->port);
@@ -670,10 +671,20 @@ static int rfcomm_tty_install(struct tty_driver *driver, struct tty_struct *tty)
 
        /* install the tty_port */
        err = tty_port_install(&dev->port, driver, tty);
-       if (err)
+       if (err) {
                rfcomm_tty_cleanup(tty);
+               return err;
+       }
 
-       return err;
+       /* take over the tty_port reference if the port was created with the
+        * flag RFCOMM_RELEASE_ONHUP. This will force the release of the port
+        * when the last process closes the tty. The behaviour is expected by
+        * userspace.
+        */
+       if (test_bit(RFCOMM_RELEASE_ONHUP, &dev->flags))
+               tty_port_put(&dev->port);
+
+       return 0;
 }
 
 static int rfcomm_tty_open(struct tty_struct *tty, struct file *filp)
@@ -1010,10 +1021,6 @@ static void rfcomm_tty_hangup(struct tty_struct *tty)
        BT_DBG("tty %p dev %p", tty, dev);
 
        tty_port_hangup(&dev->port);
-
-       if (test_bit(RFCOMM_RELEASE_ONHUP, &dev->flags) &&
-           !test_and_set_bit(RFCOMM_TTY_RELEASED, &dev->flags))
-               tty_port_put(&dev->port);
 }
 
 static int rfcomm_tty_tiocmget(struct tty_struct *tty)