USB: serial: mos7840: fix status-register error handling

commit 794744abfffef8b1f3c0c8a4896177d6d13d653d upstream.

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")
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/usb/serial/mos7840.c b/drivers/usb/serial/mos7840.c
index f2a7981ba9acd3b8aaca44478138980f114d7357..b269c37271723602bf47062ae286691bee890220 100644 (file)
--- a/drivers/usb/serial/mos7840.c
+++ b/drivers/usb/serial/mos7840.c
@@ -471,6 +471,9 @@ 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;