From 91b32f5413c17e80ac6616dd9c62e826fa438e2d Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Thu, 16 Oct 2014 16:54:27 -0400 Subject: [PATCH] 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: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/serial_core.c | 25 +++++++++++++++---------- 1 file changed, 15 insertions(+), 10 deletions(-) diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 0282eaaff517..3e36ecf98624 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -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; } -- 2.20.1