[PATCH] USB: c67x00: fix use-after-free in c67x00_add_iso_urb()

[Shuangpeng Bai <shuangpeng.kernel@gmail.com>]

When TD creation fails for the last packet of an isochronous URB,
c67x00_add_iso_urb() gives the URB back before updating the endpoint
scheduling state.

c67x00_giveback_urb() frees the URB private data, and the completion
callback may release the final URB reference. The following accesses to
urbp->ep_data, urb->interval, and urbp->cnt can therefore use freed
memory.

Update next_frame and cnt before giving back the failed final packet,
making the giveback the last operation that uses the URB and its private
data.

Fixes: e9b29ffc519b ("USB: add Cypress c67x00 OTG controller HCD driver")
Cc: stable@vger.kernel.org
Signed-off-by: Shuangpeng Bai <shuangpeng.kernel@gmail.com>
---
 drivers/usb/c67x00/c67x00-sched.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/c67x00/c67x00-sched.c b/drivers/usb/c67x00/c67x00-sched.c
index a832f5696f2a..ae6c94f41cb3 100644
--- a/drivers/usb/c67x00/c67x00-sched.c
+++ b/drivers/usb/c67x00/c67x00-sched.c
@@ -761,13 +761,13 @@ static int c67x00_add_iso_urb(struct c67x00_hcd *c67x00, struct urb *urb)
 				ret);
 			urb->iso_frame_desc[urbp->cnt].actual_length = 0;
 			urb->iso_frame_desc[urbp->cnt].status = ret;
-			if (urbp->cnt + 1 == urb->number_of_packets)
-				c67x00_giveback_urb(c67x00, urb, 0);
 		}
 
 		urbp->ep_data->next_frame =
 		    frame_add(urbp->ep_data->next_frame, urb->interval);
 		urbp->cnt++;
+		if (ret && urbp->cnt == urb->number_of_packets)
+			c67x00_giveback_urb(c67x00, urb, 0);
 	}
 	return 0;
 }
-- 
2.43.0