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Commit 91b32f54 authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
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serial: core: Fix port count when uart_open() errors 



A port count mismatch occurs if mutex_lock_interruptible()
exits uart_open() and the port has already been opened. This may
prematurely close a port on an open tty. Since uart_close() is _always_
called if uart_open() fails, the port count must be corrected if errors
occur.

Always increment the port count in uart_open(), regardless of errors;
always decrement the port count in uart_close(). Note that
tty_port_close_start() decrements the port count when uart_open()
was successful.

Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 64dbee31

drivers/tty/serial/serial_core.c

+15 −10
Original line number Diff line number Diff line
@@ -1338,8 +1338,16 @@ static void uart_close(struct tty_struct *tty, struct file *filp) 
	struct uart_port *uport;

	unsigned long flags;



	if (!state)

	if (!state) {

		struct uart_driver *drv = tty->driver->driver_state;



		state = drv->state + tty->index;

		port = &state->port;

		spin_lock_irq(&port->lock);

		--port->count;

		spin_unlock_irq(&port->lock);

		return;

	}



	uport = state->uart_port;

	port = &state->port;
@@ -1556,6 +1564,10 @@ static int uart_open(struct tty_struct *tty, struct file *filp) 


	pr_debug("uart_open(%d) called\n", line);



	spin_lock_irq(&port->lock);

	++port->count;

	spin_unlock_irq(&port->lock);



	/*

	 * We take the semaphore here to guarantee that we won't be re-entered

	 * while allocating the state structure, or while we request any IRQs
@@ -1568,17 +1580,11 @@ static int uart_open(struct tty_struct *tty, struct file *filp) 
		goto end;

	}



	port->count++;

	if (!state->uart_port || state->uart_port->flags & UPF_DEAD) {

		retval = -ENXIO;

		goto err_dec_count;

		goto err_unlock;

	}



	/*

	 * Once we set tty->driver_data here, we are guaranteed that

	 * uart_close() will decrement the driver module use count.

	 * Any failures from here onwards should not touch the count.

	 */

	tty->driver_data = state;

	state->uart_port->state = state;

	state->port.low_latency =
@@ -1599,8 +1605,7 @@ static int uart_open(struct tty_struct *tty, struct file *filp) 


end:

	return retval;

err_dec_count:

	port->count--;

err_unlock:

	mutex_unlock(&port->mutex);

	goto end;

}