[PATCH] usb: gadget: udc: fix the kernel NULL pointer in composite_setup

[He, Bo]

the patch is for fix the below kernel panic:
BUG: unable to handle kernel NULL pointer dereference at 000000000000002a
IP: [<ffffffff8170e19d>] composite_setup+0x3d/0x1830
PGD 27525b067 PUD 27525a067 PMD 0
Oops: 0002 [#1] PREEMPT SMP
Call Trace:
 [<ffffffff8168b902>] ? dwc3_trace+0x52/0x60
 [<ffffffff810c504d>] ? get_parent_ip+0xd/0x50
 [<ffffffff8171159c>] android_setup+0xbc/0x140
 [<ffffffff810ec190>] ? irq_finalize_oneshot+0xe0/0xe0
 [<ffffffff816917e7>] dwc3_ep0_delegate_req+0x37/0x50
 [<ffffffff81692e69>] dwc3_ep0_interrupt+0xaf9/0xc10
 [<ffffffff810c504d>] ? get_parent_ip+0xd/0x50
 [<ffffffff810ec190>] ? irq_finalize_oneshot+0xe0/0xe0
 [<ffffffff81690281>] dwc3_thread_interrupt+0x931/0xbf0
 [<ffffffff810ec190>] ? irq_finalize_oneshot+0xe0/0xe0
 [<ffffffff810ec1ae>] irq_thread_fn+0x1e/0x40
 [<ffffffff810ec674>] irq_thread+0x134/0x1b0
 [<ffffffff810ec260>] ? wake_threads_waitq+0x30/0x30
 [<ffffffff810b802d>] kthread+0xed/0x110
 [<ffffffff81a2fd6f>] ret_from_fork+0x3f/0x70
RIP  [<ffffffff8170e19d>] composite_setup+0x3d/0x1830

the root cause is dwc interrupt comes after usb_gadget_remove_driver.
the fix is stop udc to have the dwc3 disable the interrupt, then release
the resource in udc->driver->unbind.
usb_gadget_udc_stop-->
udc->gadget->ops->udc_stop(udc->gadget)-->
dwc3_gadget_stop

Signed-off-by: he, bo <bo.he@xxxxxxxxx>
---
 drivers/usb/gadget/udc/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
index e6f04ee..67e9aa5 100644
--- a/drivers/usb/gadget/udc/core.c
+++ b/drivers/usb/gadget/udc/core.c
@@ -1258,8 +1258,8 @@ static void usb_gadget_remove_driver(struct usb_udc *udc)
 
 	usb_gadget_disconnect(udc->gadget);
 	udc->driver->disconnect(udc->gadget);
-	udc->driver->unbind(udc->gadget);
 	usb_gadget_udc_stop(udc);
+	udc->driver->unbind(udc->gadget);
 
 	udc->driver = NULL;
 	udc->dev.driver = NULL;
-- 
2.7.4