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@xxxxxxxxxxxxxx>
Reported-by: Alexander Holler <holler@xxxxxxxxxxxxx>
---
net/bluetooth/rfcomm/tty.c | 21 ++++++++++++++-------
1 file changed, 14 insertions(+), 7 deletions(-)
diff --git a/net/bluetooth/rfcomm/tty.c b/net/bluetooth/rfcomm/tty.c
index 84fcf9f..a535ef1 100644
--- 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)
--
1.8.5.2
--
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