[Bluetooth] Hangup TTY before releasing rfcomm_dev

The core problem is that RFCOMM socket layer ioctl can release
rfcomm_dev struct while RFCOMM TTY layer is still actively using
it. Calling tty_vhangup() is needed for a synchronous hangup before
rfcomm_dev is freed.

Addresses the oops at http://bugzilla.kernel.org/show_bug.cgi?id=7509

Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/net/bluetooth/rfcomm/tty.c b/net/bluetooth/rfcomm/tty.c
index b2b1cceb102..ba469b038ea 100644
--- a/net/bluetooth/rfcomm/tty.c
+++ b/net/bluetooth/rfcomm/tty.c
@@ -383,6 +383,10 @@ static int rfcomm_release_dev(void __user *arg)
         if (req.flags & (1 << RFCOMM_HANGUP_NOW))
                 rfcomm_dlc_close(dev->dlc, 0);
 
+        /* Shut down TTY synchronously before freeing rfcomm_dev */
+        if (dev->tty)
+                tty_vhangup(dev->tty);
+
         rfcomm_dev_del(dev);
         rfcomm_dev_put(dev);
         return 0;