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 <peter@xxxxxxxxxxxxxxxxxx>
---
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 6a3571e..3f02c2b 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1337,8 +1337,16 @@ 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;
@@ -1555,6 +1563,10 @@ 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
@@ -1567,17 +1579,11 @@ 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 =
@@ -1598,8 +1604,7 @@ 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;
}
--
2.1.1
--
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