usb: gadget: udc: fotg210-udc: Fix a sleep-in-atomic-context bug in f…

…otg210_get_status()

The driver may sleep in an interrupt handler.
The function call path (from bottom to top) in Linux-4.17 is:

[FUNC] fotg210_ep_queue(GFP_KERNEL)
drivers/usb/gadget/udc/fotg210-udc.c, 744:
	fotg210_ep_queue in fotg210_get_status
drivers/usb/gadget/udc/fotg210-udc.c, 768:
	fotg210_get_status in fotg210_setup_packet
drivers/usb/gadget/udc/fotg210-udc.c, 949:
	fotg210_setup_packet in fotg210_irq (interrupt handler)

To fix this bug, GFP_KERNEL is replaced with GFP_ATOMIC.
If possible, spin_unlock() and spin_lock() around fotg210_ep_queue()
can be also removed.

This bug is found by my static analysis tool DSAC.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/gadget/udc/fotg210-udc.c

@@ -741,7 +741,7 @@ static void fotg210_get_status(struct fotg210_udc *fotg210,
 	fotg210->ep0_req->length = 2;
 
 	spin_unlock(&fotg210->lock);
-	fotg210_ep_queue(fotg210->gadget.ep0, fotg210->ep0_req, GFP_KERNEL);
+	fotg210_ep_queue(fotg210->gadget.ep0, fotg210->ep0_req, GFP_ATOMIC);
 	spin_lock(&fotg210->lock);
 }