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hso: fix crash when device disappears while serial port is open

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When the device disappear, the function hso_disconnect() is called to
perform cleanup. In the cleanup function, hso_free_interface() calls
tty_port_tty_hangup() in view of scheduling a work to hang up the tty if
needed. If the port was not open then hso_serial_ref_free() is called
directly to cleanup everything. Otherwise, hso_serial_ref_free() is called
when the last fd associated to the port is closed.

For each open port, tty_release() will call the close method,
hso_serial_close(), which drops the last kref and call
hso_serial_ref_free() which unregisters, destroys the tty port
and finally frees the structure in which the tty_port structure
is included. Later, in tty_release(), more precisely when release_tty()
is called, the tty_port previously freed is accessed to cancel
the tty buf workqueue and it leads to a crash.

In view of avoiding this crash, we add a cleanup method that is called
at the end of the hangup process and we drop the last kref in this
function when all the ports have been closed, when tty_port is no
more needed and when it is safe to free the structure containing the
tty_port structure.

Signed-off-by: Olivier Sobrie <olivier@sobrie.be>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Olivier Sobrie 2015-01-30 13:21:54 +01:00 committed by David S. Miller
parent 3ac856c100
commit 29bd3bc119
1 changed files with 13 additions and 4 deletions
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17
drivers/net/usb/hso.c
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@ -1270,7 +1270,6 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp)
goto err_out;
D1("Opening %d", serial->minor);
kref_get(&serial->parent->ref);
/* setup */
tty->driver_data = serial;
@ -1289,7 +1288,8 @@ static int hso_serial_open(struct tty_struct *tty, struct file *filp)
if (result) {
hso_stop_serial_device(serial->parent);
serial->port.count--;
kref_put(&serial->parent->ref, hso_serial_ref_free);
} else {
kref_get(&serial->parent->ref);
}
} else {
D1("Port was already open");
@ -1339,8 +1339,6 @@ static void hso_serial_close(struct tty_struct *tty, struct file *filp)
usb_autopm_put_interface(serial->parent->interface);
mutex_unlock(&serial->parent->mutex);
kref_put(&serial->parent->ref, hso_serial_ref_free);
}
/* close the requested serial port */
@ -1391,6 +1389,16 @@ static int hso_serial_write_room(struct tty_struct *tty)
return room;
}
static void hso_serial_cleanup(struct tty_struct *tty)
{
struct hso_serial *serial = tty->driver_data;
if (!serial)
return;
kref_put(&serial->parent->ref, hso_serial_ref_free);
}
/* setup the term */
static void hso_serial_set_termios(struct tty_struct *tty, struct ktermios *old)
{
@ -3214,6 +3222,7 @@ static const struct tty_operations hso_serial_ops = {
.close = hso_serial_close,
.write = hso_serial_write,
.write_room = hso_serial_write_room,
.cleanup = hso_serial_cleanup,
.ioctl = hso_serial_ioctl,
.set_termios = hso_serial_set_termios,
.chars_in_buffer = hso_serial_chars_in_buffer,