[PATCH v2] USB: misc: uss720: unregister parport on probe failure

[Myeonghun Pak <mhun512@gmail.com>]

uss720_probe() registers a parport before reading the 1284 register used
to detect unsupported Belkin F5U002 adapters. If get_1284_register()
fails, the error path drops the driver private data and the USB device
reference, but leaves the parport device registered.

Leaving the port registered is more than a private allocation leak:
parport_register_port() has already reserved a parport number and
registered the parport bus device, while pp->private_data still points at
the private data that the common error path is about to release.

Undo the pre-announce registration in the get_1284_register() failure
branch before jumping to the common private-data cleanup path. Clear
priv->pp first, matching the disconnect path and avoiding a stale pointer
in the private data.

This issue was identified during our ongoing static-analysis research while
reviewing kernel code.

Fixes: 3295f1b866bf ("usb: misc: uss720: check for incompatible versions of the Belkin F5U002")
Cc: stable@vger.kernel.org
Co-developed-by: Ijae Kim <ae878000@gmail.com>
Signed-off-by: Ijae Kim <ae878000@gmail.com>
Signed-off-by: Myeonghun Pak <mhun512@gmail.com>
---
Changes in v2:
- Move the parport cleanup to the get_1284_register() failure branch,
  as suggested by Alex.
- Clarify the visible stale registered-port effect.

 drivers/usb/misc/uss720.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/misc/uss720.c b/drivers/usb/misc/uss720.c
index a8af7615b1..bd099cd8c5 100644
--- a/drivers/usb/misc/uss720.c
+++ b/drivers/usb/misc/uss720.c
@@ -735,8 +735,11 @@ static int uss720_probe(struct usb_interface *intf,
 	 * here. */
 	ret = get_1284_register(pp, 0, &reg, GFP_KERNEL);
 	dev_dbg(&intf->dev, "reg: %7ph\n", priv->reg);
-	if (ret < 0)
+	if (ret < 0) {
+		priv->pp = NULL;
+		parport_del_port(pp);
 		goto probe_abort;
+	}
 
 	ret = usb_find_last_int_in_endpoint(interface, &epd);
 	if (!ret) {
-- 
2.47.1