tty: mxser: fix TIOCSSERIAL permission check

Changing the port type and closing_wait parameter are privileged
operations so make sure to return -EPERM if a regular user tries to
change them.

Note that the closing_wait parameter would not actually have been
changed but the return value did not indicate that.

Cc: stable@vger.kernel.org
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20210407102334.32361-15-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/mxser.c b/drivers/tty/mxser.c
index 914b230..2d8e762 100644 (file)
--- a/drivers/tty/mxser.c
+++ b/drivers/tty/mxser.c
@@ -1270,6 +1270,7 @@ static int mxser_set_serial_info(struct tty_struct *tty,
        if (!capable(CAP_SYS_ADMIN)) {
                if ((ss->baud_base != info->baud_base) ||
                                (close_delay != info->port.close_delay) ||
+                               (closing_wait != info->port.closing_wait) ||
                                ((ss->flags & ~ASYNC_USR_MASK) != (info->port.flags & ~ASYNC_USR_MASK))) {
                        mutex_unlock(&port->mutex);
                        return -EPERM;
@@ -1296,11 +1297,11 @@ static int mxser_set_serial_info(struct tty_struct *tty,
                        baud = ss->baud_base / ss->custom_divisor;
                        tty_encode_baud_rate(tty, baud, baud);
                }
-       }
 
-       info->type = ss->type;
+               info->type = ss->type;
 
-       process_txrx_fifo(info);
+               process_txrx_fifo(info);
+       }
 
        if (tty_port_initialized(port)) {
                if (flags != (port->flags & ASYNC_SPD_MASK)) {