[PATCH 4.9 29/32] usb: musb: host: fix potential NULL pointer dereference

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Bin Liu <b-liu@ti.com>

commit 2b63f1329df2cd814c1f8353fae4853ace6521d1 upstream.

musb_start_urb() doesn't check the 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.

Fixes: f283862f3b5c ("usb: musb: NAK timeout scheme on bulk TX endpoint")
Cc: stable@vger.kernel.org # v3.7+
Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/drivers/usb/musb/musb_host.c
+++ b/drivers/usb/musb/musb_host.c
@@ -1023,7 +1023,9 @@ static void musb_bulk_nak_timeout(struct
 			/* 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);
 	}
 }