[PATCH 4.4 18/25] USB: serial: spcp8x5: fix modem-status handling

Greg Kroah-Hartman
2017-02-24T08:28:36Z

From: Johan Hovold <johan@kernel.org>

commit 5ed8d41023751bdd3546f2fe4118304357efe8d2 upstream.

Make sure to detect short control transfers and return zero on success
when retrieving the modem status.

This fixes the TIOCMGET implementation which since e1ed212d8593 ("USB:
spcp8x5: add proper modem-status support") has returned TIOCM_LE on
successful retrieval, and avoids leaking bits from the stack on short
transfers.

This also fixes the carrier-detect implementation which since the above
mentioned commit unconditionally has returned true.

Fixes: e1ed212d8593 ("USB: spcp8x5: add proper modem-status support")
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/usb/serial/spcp8x5.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

--- a/drivers/usb/serial/spcp8x5.c
+++ b/drivers/usb/serial/spcp8x5.c
@@ -232,11 +232,17 @@ static int spcp8x5_get_msr(struct usb_se
ret = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
GET_UART_STATUS, GET_UART_STATUS_TYPE,
0, GET_UART_STATUS_MSR, buf, 1, 100);
- if (ret < 0)
+ if (ret < 1) {
dev_err(&port->dev, "failed to get modem status: %d\n", ret);
+ if (ret >= 0)
+ ret = -EIO;
+ goto out;
+ }

dev_dbg(&port->dev, "0xc0:0x22:0:6 %d - 0x02%x\n", ret, *buf);
*status = *buf;
+ ret = 0;
+out:
kfree(buf);

return ret;