[3/3] usb: musb: host: fix potential NULL pointer dereference

[Bin Liu <b-liu@ti.com>]

musb_start_urb() doesn't check the 3rd pass-in parameter if it is NULL.
But in musb_bulk_nak_timeout() the parameter passed to musb_start_urb()
is returned from first_qh(), which could be NULL.

So wrap the musb_start_urb() call here with a if condition check to
avoid the potential NULL pointer dereference.

Signed-off-by: Bin Liu <b-liu@ti.com>
---
v2: no changes.

 drivers/usb/musb/musb_host.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/musb/musb_host.c b/drivers/usb/musb/musb_host.c
index e50438ae241e..218aadef5bbf 100644
--- a/drivers/usb/musb/musb_host.c
+++ b/drivers/usb/musb/musb_host.c
@@ -990,7 +990,9 @@ static void musb_bulk_nak_timeout(struct musb *musb, struct musb_hw_ep *ep,
 			/* set tx_reinit and schedule the next qh */
 			ep->tx_reinit = 1;
 		}
-		musb_start_urb(musb, is_in, next_qh);
+
+		if (next_qh)
+			musb_start_urb(musb, is_in, next_qh);
 	}
 }