[PATCH] usb: cdnsp: Fix potential dereference of NULL pointer

[Yongzhi Liu]

The return value of cdnsp_get_transfer_ring()
needs to be checked to avoid use of NULL pointer
in case of an acquisition failure.

Fixes: 3d8290455 ("usb: cdnsp: cdns3 Add main part of Cadence USBSSP DRD Driver")

Signed-off-by: Yongzhi Liu <lyz_cs@xxxxxxxxxx>
---
 drivers/usb/cdns3/cdnsp-ring.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/usb/cdns3/cdnsp-ring.c b/drivers/usb/cdns3/cdnsp-ring.c
index 1b14384..9f206b9 100644
--- a/drivers/usb/cdns3/cdnsp-ring.c
+++ b/drivers/usb/cdns3/cdnsp-ring.c
@@ -655,6 +655,8 @@ static int cdnsp_cmd_set_deq(struct cdnsp_device *pdev,
 	 * to reflect the new position.
 	 */
 	ep_ring = cdnsp_get_transfer_ring(pdev, pep, deq_state->stream_id);
+	if (!ep_ring)
+		return -EINVAL;
 
 	if (cdnsp_trb_is_link(ep_ring->dequeue)) {
 		ep_ring->deq_seg = ep_ring->deq_seg->next;
-- 
2.7.4