tty: moxa: fix TIOCSSERIAL implementation

TIOCSSERIAL is a horrid, underspecified, legacy interface which for most
serial devices is only useful for setting the close_delay and
closing_wait parameters.

A non-privileged user has only ever been able to set the since long
deprecated ASYNC_SPD flags and trying to change any other *supported*
feature should result in -EPERM being returned. Setting the current
values for any supported features should return success.

Fix the moxa implementation which was returning -EPERM also for a
privileged user when trying to change certain unsupported parameters and
instead return success consistently.

Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20210407102334.32361-13-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/moxa.c b/drivers/tty/moxa.c
index 63e440d900ffca9d6f283590b249126c57508d56..4d4f15b5cd29819a0ced008d1069a364202317f7 100644 (file)
--- a/drivers/tty/moxa.c
+++ b/drivers/tty/moxa.c
@@ -2055,11 +2055,6 @@ static int moxa_set_serial_info(struct tty_struct *tty,
        if (!info)
                return -ENODEV;
 
-       if (ss->irq != 0 || ss->port != 0 ||
-                       ss->custom_divisor != 0 ||
-                       ss->baud_base != 921600)
-               return -EPERM;
-
        close_delay = msecs_to_jiffies(ss->close_delay * 10);
 
        mutex_lock(&info->port.mutex);