[PATCH 2/4] USB: serial: mos7840: fix status-register error handling

[Johan Hovold <johan@kernel.org>]

Add missing transfer-length sanity check to the status-register
completion handler to avoid leaking bits of uninitialised slab data to
user space.

Fixes: 3f5429746d91 ("USB: Moschip 7840 USB-Serial Driver")
Cc: stable <stable@vger.kernel.org>     # 2.6.19
Cc: Paul B Schroeder <pschroeder@uplogix.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/serial/mos7840.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/usb/serial/mos7840.c b/drivers/usb/serial/mos7840.c
index fdceb46d9fc6..b580b4c7fa48 100644
--- a/drivers/usb/serial/mos7840.c
+++ b/drivers/usb/serial/mos7840.c
@@ -468,6 +468,9 @@ static void mos7840_control_callback(struct urb *urb)
 	}
 
 	dev_dbg(dev, "%s urb buffer size is %d\n", __func__, urb->actual_length);
+	if (urb->actual_length < 1)
+		goto out;
+
 	dev_dbg(dev, "%s mos7840_port->MsrLsr is %d port %d\n", __func__,
 		mos7840_port->MsrLsr, mos7840_port->port_num);
 	data = urb->transfer_buffer;
-- 
2.18.0