USB: serial: cp210x: fix flow-control error handling

Make sure that the driver crtscts state is not updated in the unlikely
event that the flow-control request fails. Not doing so could break RTS
control.

Fixes: 5951b8508855 ("USB: serial: cp210x: suppress modem-control errors")
Cc: stable@vger.kernel.org	# 5.11
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>

diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index ad6aeb4..d48bed5 100644 (file)
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -1190,6 +1190,7 @@ static void cp210x_set_flow_control(struct tty_struct *tty,
        struct cp210x_flow_ctl flow_ctl;
        u32 flow_repl;
        u32 ctl_hs;
+       bool crtscts;
        int ret;
 
        /*
@@ -1249,14 +1250,14 @@ static void cp210x_set_flow_control(struct tty_struct *tty,
                        flow_repl |= CP210X_SERIAL_RTS_FLOW_CTL;
                else
                        flow_repl |= CP210X_SERIAL_RTS_INACTIVE;
-               port_priv->crtscts = true;
+               crtscts = true;
        } else {
                ctl_hs &= ~CP210X_SERIAL_CTS_HANDSHAKE;
                if (port_priv->rts)
                        flow_repl |= CP210X_SERIAL_RTS_ACTIVE;
                else
                        flow_repl |= CP210X_SERIAL_RTS_INACTIVE;
-               port_priv->crtscts = false;
+               crtscts = false;
        }
 
        if (I_IXOFF(tty)) {
@@ -1279,8 +1280,12 @@ static void cp210x_set_flow_control(struct tty_struct *tty,
        flow_ctl.ulControlHandshake = cpu_to_le32(ctl_hs);
        flow_ctl.ulFlowReplace = cpu_to_le32(flow_repl);
 
-       cp210x_write_reg_block(port, CP210X_SET_FLOW, &flow_ctl,
+       ret = cp210x_write_reg_block(port, CP210X_SET_FLOW, &flow_ctl,
                        sizeof(flow_ctl));
+       if (ret)
+               goto out_unlock;
+
+       port_priv->crtscts = crtscts;
 out_unlock:
        mutex_unlock(&port_priv->mutex);
 }