[PATCH] usb: Add data checks in usbtmc_disconnect

[Lv Yunlong]

In usbtmc_disconnect, data is got from intf with the
initial reference. There is no refcount inc operation
before usbmc_free_int(data). In usbmc_free_int(data),
the data may be freed.

But later in usbtmc_disconnect, there is another put
function of data. I think it is better to add necessary
checks to avoid the data being put twice. It could cause
errors in race.

Signed-off-by: Lv Yunlong <lyl2...@mail.ustc.edu.cn>
---
 drivers/usb/class/usbtmc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c
index 74d5a9c5238a..e0438cb46386 100644
--- a/drivers/usb/class/usbtmc.c
+++ b/drivers/usb/class/usbtmc.c
@@ -2494,7 +2494,9 @@ static void usbtmc_disconnect(struct usb_interface *intf)
        }
        mutex_unlock(&data->io_mutex);
        usbtmc_free_int(data);
-       kref_put(&data->kref, usbtmc_delete);
+
+       if (data->iin_ep_present && data->iin_urb)
+               kref_put(&data->kref, usbtmc_delete);
 }
 
 static void usbtmc_draw_down(struct usbtmc_file_data *file_data)
-- 
2.25.1