tty: serial - fix various misuses/mishandlings of port->tty

Make it robust against hang up events. In most cases we can do this simply
by passing the right things in the first place.
Signed-off-by: Alan Cox <alan@linux.intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/serial/serial_core.c

@@ -58,7 +58,7 @@ static struct lock_class_key port_lock_key;
 #define uart_console(port)	(0)
 #endif
 
-static void uart_change_speed(struct uart_state *state,
+static void uart_change_speed(struct tty_struct *tty, struct uart_state *state,
 					struct ktermios *old_termios);
 static void uart_wait_until_sent(struct tty_struct *tty, int timeout);
 static void uart_change_pm(struct uart_state *state, int pm_state);
@@ -137,7 +137,7 @@ uart_update_mctrl(struct uart_port *port, unsigned int set, unsigned int clear)
  * Startup the port.  This will be called once per open.  All calls
  * will be serialised by the per-port mutex.
  */
-static int uart_startup(struct uart_state *state, int init_hw)
+static int uart_startup(struct tty_struct *tty, struct uart_state *state, int init_hw)
 {
 	struct uart_port *uport = state->uart_port;
 	struct tty_port *port = &state->port;
@@ -152,7 +152,7 @@ static int uart_startup(struct uart_state *state, int init_hw)
 	 * once we have successfully opened the port.  Also set
 	 * up the tty->alt_speed kludge
 	 */
-	set_bit(TTY_IO_ERROR, &port->tty->flags);
+	set_bit(TTY_IO_ERROR, &tty->flags);
 
 	if (uport->type == PORT_UNKNOWN)
 		return 0;
@@ -177,26 +177,26 @@ static int uart_startup(struct uart_state *state, int init_hw)
 			/*
 			 * Initialise the hardware port settings.
 			 */
-			uart_change_speed(state, NULL);
+			uart_change_speed(tty, state, NULL);
 
 			/*
 			 * Setup the RTS and DTR signals once the
 			 * port is open and ready to respond.
 			 */
-			if (port->tty->termios->c_cflag & CBAUD)
+			if (tty->termios->c_cflag & CBAUD)
 				uart_set_mctrl(uport, TIOCM_RTS | TIOCM_DTR);
 		}
 
 		if (port->flags & ASYNC_CTS_FLOW) {
 			spin_lock_irq(&uport->lock);
 			if (!(uport->ops->get_mctrl(uport) & TIOCM_CTS))
-				port->tty->hw_stopped = 1;
+				tty->hw_stopped = 1;
 			spin_unlock_irq(&uport->lock);
 		}
 
 		set_bit(ASYNCB_INITIALIZED, &port->flags);
 
-		clear_bit(TTY_IO_ERROR, &port->tty->flags);
+		clear_bit(TTY_IO_ERROR, &tty->flags);
 	}
 
 	if (retval && capable(CAP_SYS_ADMIN))
@@ -210,11 +210,10 @@ static int uart_startup(struct uart_state *state, int init_hw)
  * DTR is dropped if the hangup on close termio flag is on.  Calls to
  * uart_shutdown are serialised by the per-port semaphore.
  */
-static void uart_shutdown(struct uart_state *state)
+static void uart_shutdown(struct tty_struct *tty, struct uart_state *state)
 {
 	struct uart_port *uport = state->uart_port;
 	struct tty_port *port = &state->port;
-	struct tty_struct *tty = port->tty;
 
 	/*
 	 * Set the TTY IO error marker
@@ -430,11 +429,10 @@ uart_get_divisor(struct uart_port *port, unsigned int baud)
 EXPORT_SYMBOL(uart_get_divisor);
 
 /* FIXME: Consistent locking policy */
-static void
-uart_change_speed(struct uart_state *state, struct ktermios *old_termios)
+static void uart_change_speed(struct tty_struct *tty, struct uart_state *state,
+					struct ktermios *old_termios)
 {
 	struct tty_port *port = &state->port;
-	struct tty_struct *tty = port->tty;
 	struct uart_port *uport = state->uart_port;
 	struct ktermios *termios;
 
@@ -463,8 +461,8 @@ uart_change_speed(struct uart_state *state, struct ktermios *old_termios)
 	uport->ops->set_termios(uport, termios, old_termios);
 }
 
-static inline int
-__uart_put_char(struct uart_port *port, struct circ_buf *circ, unsigned char c)
+static inline int __uart_put_char(struct uart_port *port,
+				struct circ_buf *circ, unsigned char c)
 {
 	unsigned long flags;
 	int ret = 0;
@@ -494,8 +492,8 @@ static void uart_flush_chars(struct tty_struct *tty)
 	uart_start(tty);
 }
 
-static int
-uart_write(struct tty_struct *tty, const unsigned char *buf, int count)
+static int uart_write(struct tty_struct *tty,
+					const unsigned char *buf, int count)
 {
 	struct uart_state *state = tty->driver_data;
 	struct uart_port *port;
@@ -675,7 +673,7 @@ static int uart_get_info(struct uart_state *state,
 	return 0;
 }
 
-static int uart_set_info(struct uart_state *state,
+static int uart_set_info(struct tty_struct *tty, struct uart_state *state,
 			 struct serial_struct __user *newinfo)
 {
 	struct serial_struct new_serial;
@@ -770,7 +768,7 @@ static int uart_set_info(struct uart_state *state,
 		 * We need to shutdown the serial port at the old
 		 * port/type/irq combination.
 		 */
-		uart_shutdown(state);
+		uart_shutdown(tty, state);
 	}
 
 	if (change_port) {
@@ -869,25 +867,27 @@ static int uart_set_info(struct uart_state *state,
 				       "is deprecated.\n", current->comm,
 				       tty_name(port->tty, buf));
 			}
-			uart_change_speed(state, NULL);
+			uart_change_speed(tty, state, NULL);
 		}
 	} else
-		retval = uart_startup(state, 1);
+		retval = uart_startup(tty, state, 1);
  exit:
 	mutex_unlock(&port->mutex);
 	return retval;
 }
 
-
-/*
- * uart_get_lsr_info - get line status register info.
- * Note: uart_ioctl protects us against hangups.
+/**
+ *	uart_get_lsr_info	-	get line status register info
+ *	@tty: tty associated with the UART
+ *	@state: UART being queried
+ *	@value: returned modem value
+ *
+ *	Note: uart_ioctl protects us against hangups.
  */
-static int uart_get_lsr_info(struct uart_state *state,
-			     unsigned int __user *value)
+static int uart_get_lsr_info(struct tty_struct *tty,
+			struct uart_state *state, unsigned int __user *value)
 {
 	struct uart_port *uport = state->uart_port;
-	struct tty_port *port = &state->port;
 	unsigned int result;
 
 	result = uport->ops->tx_empty(uport);
@@ -900,7 +900,7 @@ static int uart_get_lsr_info(struct uart_state *state,
 	 */
 	if (uport->x_char ||
 	    ((uart_circ_chars_pending(&state->xmit) > 0) &&
-	     !port->tty->stopped && !port->tty->hw_stopped))
+	     !tty->stopped && !tty->hw_stopped))
 		result &= ~TIOCSER_TEMT;
 
 	return put_user(result, value);
@@ -961,7 +961,7 @@ static int uart_break_ctl(struct tty_struct *tty, int break_state)
 	return 0;
 }
 
-static int uart_do_autoconfig(struct uart_state *state)
+static int uart_do_autoconfig(struct tty_struct *tty,struct uart_state *state)
 {
 	struct uart_port *uport = state->uart_port;
 	struct tty_port *port = &state->port;
@@ -980,7 +980,7 @@ static int uart_do_autoconfig(struct uart_state *state)
 
 	ret = -EBUSY;
 	if (tty_port_users(port) == 1) {
-		uart_shutdown(state);
+		uart_shutdown(tty, state);
 
 		/*
 		 * If we already have a port type configured,
@@ -999,7 +999,7 @@ static int uart_do_autoconfig(struct uart_state *state)
 		 */
 		uport->ops->config_port(uport, flags);
 
-		ret = uart_startup(state, 1);
+		ret = uart_startup(tty, state, 1);
 	}
 	mutex_unlock(&port->mutex);
 	return ret;
@@ -1122,11 +1122,11 @@ uart_ioctl(struct tty_struct *tty, struct file *filp, unsigned int cmd,
 		break;
 
 	case TIOCSSERIAL:
-		ret = uart_set_info(state, uarg);
+		ret = uart_set_info(tty, state, uarg);
 		break;
 
 	case TIOCSERCONFIG:
-		ret = uart_do_autoconfig(state);
+		ret = uart_do_autoconfig(tty, state);
 		break;
 
 	case TIOCSERGWILD: /* obsolete */
@@ -1172,7 +1172,7 @@ uart_ioctl(struct tty_struct *tty, struct file *filp, unsigned int cmd,
 	 */
 	switch (cmd) {
 	case TIOCSERGETLSR: /* Get line status register */
-		ret = uart_get_lsr_info(state, uarg);
+		ret = uart_get_lsr_info(tty, state, uarg);
 		break;
 
 	default: {
@@ -1219,7 +1219,7 @@ static void uart_set_termios(struct tty_struct *tty,
 		return;
 	}
 
-	uart_change_speed(state, old_termios);
+	uart_change_speed(tty, state, old_termios);
 
 	/* Handle transition to B0 status */
 	if ((old_termios->c_cflag & CBAUD) && !(cflag & CBAUD))
@@ -1335,7 +1335,7 @@ static void uart_close(struct tty_struct *tty, struct file *filp)
 		uart_wait_until_sent(tty, uport->timeout);
 	}
 
-	uart_shutdown(state);
+	uart_shutdown(tty, state);
 	uart_flush_buffer(tty);
 
 	tty_ldisc_flush(tty);
@@ -1436,7 +1436,7 @@ static void uart_hangup(struct tty_struct *tty)
 	mutex_lock(&port->mutex);
 	if (port->flags & ASYNC_NORMAL_ACTIVE) {
 		uart_flush_buffer(tty);
-		uart_shutdown(state);
+		uart_shutdown(tty, state);
 		port->count = 0;
 		clear_bit(ASYNCB_NORMAL_ACTIVE, &port->flags);
 		tty_port_tty_set(port, NULL);
@@ -1446,15 +1446,19 @@ static void uart_hangup(struct tty_struct *tty)
 	mutex_unlock(&port->mutex);
 }
 
-/*
- * Copy across the serial console cflag setting into the termios settings
- * for the initial open of the port.  This allows continuity between the
- * kernel settings, and the settings init adopts when it opens the port
- * for the first time.
+/**
+ *	uart_update_termios	-	update the terminal hw settings
+ *	@tty: tty associated with UART
+ *	@state: UART to update
+ *
+ *	Copy across the serial console cflag setting into the termios settings
+ *	for the initial open of the port.  This allows continuity between the
+ *	kernel settings, and the settings init adopts when it opens the port
+ *	for the first time.
  */
-static void uart_update_termios(struct uart_state *state)
+static void uart_update_termios(struct tty_struct *tty,
+						struct uart_state *state)
 {
-	struct tty_struct *tty = state->port.tty;
 	struct uart_port *port = state->uart_port;
 
 	if (uart_console(port) && port->cons->cflag) {
@@ -1471,7 +1475,7 @@ static void uart_update_termios(struct uart_state *state)
 		/*
 		 * Make termios settings take effect.
 		 */
-		uart_change_speed(state, NULL);
+		uart_change_speed(tty, state, NULL);
 
 		/*
 		 * And finally enable the RTS and DTR signals.
@@ -1668,7 +1672,7 @@ static int uart_open(struct tty_struct *tty, struct file *filp)
 	/*
 	 * Start up the serial port.
 	 */
-	retval = uart_startup(state, 0);
+	retval = uart_startup(tty, state, 0);
 
 	/*
 	 * If we succeeded, wait until the port is ready.
@@ -1683,7 +1687,7 @@ static int uart_open(struct tty_struct *tty, struct file *filp)
 	if (retval == 0 && !(port->flags & ASYNC_NORMAL_ACTIVE)) {
 		set_bit(ASYNCB_NORMAL_ACTIVE, &port->flags);
 
-		uart_update_termios(state);
+		uart_update_termios(tty, state);
 	}
 
 fail:
@@ -2010,9 +2014,13 @@ int uart_suspend_port(struct uart_driver *drv, struct uart_port *uport)
 	struct tty_port *port = &state->port;
 	struct device *tty_dev;
 	struct uart_match match = {uport, drv};
+	struct tty_struct *tty;
 
 	mutex_lock(&port->mutex);
 
+	/* Must be inside the mutex lock until we convert to tty_port */
+	tty = port->tty;
+
 	tty_dev = device_find_child(uport->dev, &match, serial_match_port);
 	if (device_may_wakeup(tty_dev)) {
 		enable_irq_wake(uport->irq);
@@ -2105,9 +2113,12 @@ int uart_resume_port(struct uart_driver *drv, struct uart_port *uport)
 		ops->set_mctrl(uport, 0);
 		spin_unlock_irq(&uport->lock);
 		if (console_suspend_enabled || !uart_console(uport)) {
+			/* Protected by port mutex for now */
+			struct tty_struct *tty = port->tty;
 			ret = ops->startup(uport);
 			if (ret == 0) {
-				uart_change_speed(state, NULL);
+				if (tty)
+					uart_change_speed(tty, state, NULL);
 				spin_lock_irq(&uport->lock);
 				ops->set_mctrl(uport, uport->mctrl);
 				ops->start_tx(uport);
@@ -2119,7 +2130,7 @@ int uart_resume_port(struct uart_driver *drv, struct uart_port *uport)
 				 * Clear the "initialized" flag so we won't try
 				 * to call the low level drivers shutdown method.
 				 */
-				uart_shutdown(state);
+				uart_shutdown(tty, state);
 			}
 		}