This patch (as1229) fixes a few lifetime and locking problems in the usb-serial driver. The main symptom is that an invalid kevent is created when the serial device is unplugged while a connection is active. Ports should be unregistered when device is disconnected, not when the parent usb_serial structure is deallocated. Each open file should hold a reference to the corresponding port structure, and the reference should be released when the file is closed. serial->disc_mutex should be acquired in serial_open(), to resolve the classic race between open and disconnect. serial_close() doesn't need to hold both serial->disc_mutex and port->mutex at the same time. Release the subdriver's module reference only after releasing all the other references, in case one of the release routines needs to invoke some code in the subdriver module. Replace a call to flush_scheduled_work() (which is prone to deadlocks) with cancel_work_sync(). Also, add a call to cancel_work_sync() in the disconnect routine. Reduce the scope of serial->disc_mutex in serial_disconnect(). The only place it really needs to protect is where the "disconnected" flag is set. This fixes the bug reported in http://bugs.freedesktop.org/show_bug.cgi?id=20703 Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> Tested-by: Dan Williams <dcbw@xxxxxxxxxx> Reviewed-by: Oliver Neukum <oliver@xxxxxxxxxx> --- The version that was tested and reviewed wasn't quite the same as this one, but it was pretty close. Similar patches will be submitted for the .stable kernels after this one is accepted. Because of other changes, this one can't be applied verbatim. Index: usb-2.6/drivers/usb/serial/usb-serial.c =================================================================== --- usb-2.6.orig/drivers/usb/serial/usb-serial.c +++ usb-2.6/drivers/usb/serial/usb-serial.c @@ -142,16 +142,6 @@ static void destroy_serial(struct kref * if (serial->minor != SERIAL_TTY_NO_MINOR) return_serial(serial); - for (i = 0; i < serial->num_ports; ++i) - serial->port[i]->port.count = 0; - - /* the ports are cleaned up and released in port_release() */ - for (i = 0; i < serial->num_ports; ++i) - if (serial->port[i]->dev.parent != NULL) { - device_unregister(&serial->port[i]->dev); - serial->port[i] = NULL; - } - /* If this is a "fake" port, we have to clean it up here, as it will * not get cleaned up in port_release() as it was never registered with * the driver core */ @@ -186,7 +176,7 @@ static int serial_open (struct tty_struc struct usb_serial *serial; struct usb_serial_port *port; unsigned int portNumber; - int retval; + int retval = 0; dbg("%s", __func__); @@ -197,21 +187,24 @@ static int serial_open (struct tty_struc return -ENODEV; } + mutex_lock(&serial->disc_mutex); portNumber = tty->index - serial->minor; port = serial->port[portNumber]; - if (!port) { - retval = -ENODEV; - goto bailout_kref_put; - } - - if (port->serial->disconnected) { + if (!port || serial->disconnected) retval = -ENODEV; - goto bailout_kref_put; - } + else + get_device(&port->dev); + /* + * Note: Our locking order requirement does not allow port->mutex + * to be acquired while serial->disc_mutex is held. + */ + mutex_unlock(&serial->disc_mutex); + if (retval) + goto bailout_serial_put; if (mutex_lock_interruptible(&port->mutex)) { retval = -ERESTARTSYS; - goto bailout_kref_put; + goto bailout_port_put; } ++port->port.count; @@ -231,14 +224,20 @@ static int serial_open (struct tty_struc goto bailout_mutex_unlock; } - retval = usb_autopm_get_interface(serial->interface); + mutex_lock(&serial->disc_mutex); + if (serial->disconnected) + retval = -ENODEV; + else + retval = usb_autopm_get_interface(serial->interface); if (retval) goto bailout_module_put; + /* only call the device specific open if this * is the first time the port is opened */ retval = serial->type->open(tty, port, filp); if (retval) goto bailout_interface_put; + mutex_unlock(&serial->disc_mutex); } mutex_unlock(&port->mutex); @@ -247,13 +246,16 @@ static int serial_open (struct tty_struc bailout_interface_put: usb_autopm_put_interface(serial->interface); bailout_module_put: + mutex_unlock(&serial->disc_mutex); module_put(serial->type->driver.owner); bailout_mutex_unlock: port->port.count = 0; tty->driver_data = NULL; tty_port_tty_set(&port->port, NULL); mutex_unlock(&port->mutex); -bailout_kref_put: +bailout_port_put: + put_device(&port->dev); +bailout_serial_put: usb_serial_put(serial); return retval; } @@ -261,6 +263,9 @@ bailout_kref_put: static void serial_close(struct tty_struct *tty, struct file *filp) { struct usb_serial_port *port = tty->driver_data; + struct usb_serial *serial; + struct module *owner; + int count; if (!port) return; @@ -268,6 +273,8 @@ static void serial_close(struct tty_stru dbg("%s - port %d", __func__, port->number); mutex_lock(&port->mutex); + serial = port->serial; + owner = serial->type->driver.owner; if (port->port.count == 0) { mutex_unlock(&port->mutex); @@ -280,7 +287,7 @@ static void serial_close(struct tty_stru * this before we drop the port count. The call is protected * by the port mutex */ - port->serial->type->close(tty, port, filp); + serial->type->close(tty, port, filp); if (port->port.count == (port->console ? 2 : 1)) { struct tty_struct *tty = tty_port_tty_get(&port->port); @@ -294,17 +301,23 @@ static void serial_close(struct tty_stru } } - if (port->port.count == 1) { - mutex_lock(&port->serial->disc_mutex); - if (!port->serial->disconnected) - usb_autopm_put_interface(port->serial->interface); - mutex_unlock(&port->serial->disc_mutex); - module_put(port->serial->type->driver.owner); - } --port->port.count; - + count = port->port.count; mutex_unlock(&port->mutex); - usb_serial_put(port->serial); + put_device(&port->dev); + + /* Mustn't dereference port any more */ + if (count == 0) { + mutex_lock(&serial->disc_mutex); + if (!serial->disconnected) + usb_autopm_put_interface(serial->interface); + mutex_unlock(&serial->disc_mutex); + } + usb_serial_put(serial); + + /* Mustn't dereference serial any more */ + if (count == 0) + module_put(owner); } static int serial_write(struct tty_struct *tty, const unsigned char *buf, @@ -553,7 +566,13 @@ static void kill_traffic(struct usb_seri static void port_free(struct usb_serial_port *port) { + /* + * Stop all the traffic before cancelling the work, so that + * nobody will restart it by calling usb_serial_port_softint. + */ kill_traffic(port); + cancel_work_sync(&port->work); + usb_free_urb(port->read_urb); usb_free_urb(port->write_urb); usb_free_urb(port->interrupt_in_urb); @@ -562,7 +581,6 @@ static void port_free(struct usb_serial_ kfree(port->bulk_out_buffer); kfree(port->interrupt_in_buffer); kfree(port->interrupt_out_buffer); - flush_scheduled_work(); /* port->work */ kfree(port); } @@ -1047,6 +1065,8 @@ void usb_serial_disconnect(struct usb_in usb_set_intfdata(interface, NULL); /* must set a flag, to signal subdrivers */ serial->disconnected = 1; + mutex_unlock(&serial->disc_mutex); + for (i = 0; i < serial->num_ports; ++i) { port = serial->port[i]; if (port) { @@ -1056,11 +1076,13 @@ void usb_serial_disconnect(struct usb_in tty_kref_put(tty); } kill_traffic(port); + cancel_work_sync(&port->work); + device_unregister(&port->dev); + serial->port[i] = NULL; } } /* let the last holder of this object * cause it to be cleaned up */ - mutex_unlock(&serial->disc_mutex); usb_serial_put(serial); dev_info(dev, "device disconnected\n"); } -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
