serial: sifive: lock port in startup()/shutdown() callbacks

startup()/shutdown() callbacks access SIFIVE_SERIAL_IE_OFFS.
The register is also accessed from write() callback.

If console were printing and startup()/shutdown() callback
gets called, its access to the register could be overwritten.

Add port->lock to startup()/shutdown() callbacks to make sure
their access to SIFIVE_SERIAL_IE_OFFS is synchronized against
write() callback.

Fixes: 45c054d0815b ("tty: serial: add driver for the SiFive UART")
Signed-off-by: Ryo Takakura <ryotkkr98@gmail.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: stable@vger.kernel.org
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Rule: add
Link: https://lore.kernel.org/stable/20250330003522.386632-1-ryotkkr98%40gmail.com
Link: https://lore.kernel.org/r/20250412001847.183221-1-ryotkkr98@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/sifive.c b/drivers/tty/serial/sifive.c
index 5904a2d4cefa71d371c3d6a07c66cae9140d0353..054a8e630aceac4dd40d70b47bf9d5b2edc61618 100644 (file)
--- a/drivers/tty/serial/sifive.c
+++ b/drivers/tty/serial/sifive.c
@@ -563,8 +563,11 @@ static void sifive_serial_break_ctl(struct uart_port *port, int break_state)
 static int sifive_serial_startup(struct uart_port *port)
 {
        struct sifive_serial_port *ssp = port_to_sifive_serial_port(port);
+       unsigned long flags;
 
+       uart_port_lock_irqsave(&ssp->port, &flags);
        __ssp_enable_rxwm(ssp);
+       uart_port_unlock_irqrestore(&ssp->port, flags);
 
        return 0;
 }
@@ -572,9 +575,12 @@ static int sifive_serial_startup(struct uart_port *port)
 static void sifive_serial_shutdown(struct uart_port *port)
 {
        struct sifive_serial_port *ssp = port_to_sifive_serial_port(port);
+       unsigned long flags;
 
+       uart_port_lock_irqsave(&ssp->port, &flags);
        __ssp_disable_rxwm(ssp);
        __ssp_disable_txwm(ssp);
+       uart_port_unlock_irqrestore(&ssp->port, flags);
 }
 
 /**