serial: 8250: Prevent concurrent updates to shadow registers

The port shadow registers, ->fcr and ->mcr, must be protected from
concurrent updates. Relocate the shadow register updates in
serial8250_do_set_termios() to the port lock critical section.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 9 insertions, 9 deletions

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index 1449c56506b7..57d13b058a48 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -2549,6 +2549,15 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
                                   port->uartclk / 16);
         quot = serial8250_get_divisor(up, baud, &frac);
 
+        /*
+         * Ok, we're now changing the port state.  Do it with
+         * interrupts disabled.
+         */
+        serial8250_rpm_get(up);
+        spin_lock_irqsave(&port->lock, flags);
+
+        up->lcr = cval;                                 /* Save computed LCR */
+
         if (up->capabilities & UART_CAP_FIFO && port->fifosize > 1) {
                 /* NOTE: If fifo_bug is not set, a user can set RX_trigger. */
                 if ((baud < 2400 && !up->dma) || up->fifo_bug) {
@@ -2572,15 +2581,6 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
         }
 
         /*
-         * Ok, we're now changing the port state.  Do it with
-         * interrupts disabled.
-         */
-        serial8250_rpm_get(up);
-        spin_lock_irqsave(&port->lock, flags);
-
-        up->lcr = cval;                                 /* Save computed LCR */
-
-        /*
          * Update the per-port timeout.
          */
         uart_update_timeout(port, termios->c_cflag, baud);