tty, serial: Fix race and NULL check in uart_close()

Commit 46d57a449aa1 ("serial: use tty_port pointers in the core code")
contained two bugs that causes (rare) crashes:

 - the rename typoed one site

 - a NULL check was missed

Reported-and-tested-by: Ingo Molnar <mingo@elte.hu>
Cc: Greg KH <gregkh@suse.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 2 deletions

diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
index 1689bda1d13b..dcc72444e8e7 100644
--- a/drivers/serial/serial_core.c
+++ b/drivers/serial/serial_core.c
@@ -1270,6 +1270,9 @@ static void uart_close(struct tty_struct *tty, struct file *filp)
 
         BUG_ON(!kernel_locked());
 
+        if (!state)
+                return;
+
         uport = state->uart_port;
         port = &state->port;
 
@@ -1316,9 +1319,9 @@ static void uart_close(struct tty_struct *tty, struct file *filp)
          */
         if (port->flags & ASYNC_INITIALIZED) {
                 unsigned long flags;
-                spin_lock_irqsave(&port->lock, flags);
+                spin_lock_irqsave(&uport->lock, flags);
                 uport->ops->stop_rx(uport);
-                spin_unlock_irqrestore(&port->lock, flags);
+                spin_unlock_irqrestore(&uport->lock, flags);
                 /*
                  * Before we drop DTR, make sure the UART transmitter
                  * has completely drained; this is especially