[PATCH stable-4.4] USB: serial: cp210x: fix tiocmget error handling

[Johan Hovold <johan@kernel.org>]

commit de24e0a108bc48062e1c7acaa97014bce32a919f upstream.

The current tiocmget implementation would fail to report errors up the
stack and instead leaked a few bits from the stack as a mask of
modem-status flags.

Fixes: 39a66b8d22a3 ("[PATCH] USB: CP2101 Add support for flow control")
Signed-off-by: Johan Hovold <johan@kernel.org>
---

Here's a backport of de24e0a108bc ("USB: serial: cp210x: fix tiocmget
error handling") to 4.4.

Johan


 drivers/usb/serial/cp210x.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c
index 6eccded3bc33..976195e748a3 100644
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -845,7 +845,9 @@ static int cp210x_tiocmget(struct tty_struct *tty)
 	unsigned int control;
 	int result;
 
-	cp210x_get_config(port, CP210X_GET_MDMSTS, &control, 1);
+	result = cp210x_get_config(port, CP210X_GET_MDMSTS, &control, 1);
+	if (result)
+		return result;
 
 	result = ((control & CONTROL_DTR) ? TIOCM_DTR : 0)
 		|((control & CONTROL_RTS) ? TIOCM_RTS : 0)
-- 
2.7.3