serial: 8250_fsl: fix handle_irq locking

The 8250 handle_irq callback is not just called from the interrupt
handler but also from a timer callback when polling (e.g. for ports
without an interrupt line). Consequently the callback must explicitly
disable interrupts to avoid a potential deadlock with another interrupt
in polled mode.

Fix up the two paths in the freescale callback that failed to re-enable
interrupts when polling.

Fixes: 853a9ae29e97 ("serial: 8250: fix handle_irq locking")
Cc: stable@vger.kernel.org	# 5.13
Reported-by: Dan Carpenter <error27@gmail.com>
Link: https://lore.kernel.org/r/Y/xYzqp4ogmOF5t0@kili
Signed-off-by: Johan Hovold <johan@kernel.org>
Acked-by: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20230227085046.24282-1-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/8250/8250_fsl.c b/drivers/tty/serial/8250/8250_fsl.c
index 8aad15622a2e5c869b94dfec762f98185e1d785e..8adfaa183f778d4a6f8cf21098025b2dac886691 100644 (file)
--- a/drivers/tty/serial/8250/8250_fsl.c
+++ b/drivers/tty/serial/8250/8250_fsl.c
@@ -34,7 +34,7 @@ int fsl8250_handle_irq(struct uart_port *port)
 
        iir = port->serial_in(port, UART_IIR);
        if (iir & UART_IIR_NO_INT) {
-               spin_unlock(&up->port.lock);
+               spin_unlock_irqrestore(&up->port.lock, flags);
                return 0;
        }
 
@@ -42,7 +42,7 @@ int fsl8250_handle_irq(struct uart_port *port)
        if (unlikely(up->lsr_saved_flags & UART_LSR_BI)) {
                up->lsr_saved_flags &= ~UART_LSR_BI;
                port->serial_in(port, UART_RX);
-               spin_unlock(&up->port.lock);
+               spin_unlock_irqrestore(&up->port.lock, flags);
                return 1;
        }