wdm_in_callback() is a completion handler function for the USB driver.
So it should not sleep. But it calls service_outstanding_interrupt(), 
which calls usb_submit_urb() with GFP_KERNEL. 

To fix this bug, GFP_KERNEL is replaced with GFP_ATOMIC.

This bug is found by my static analysis tool DSAC.

Signed-off-by: Jia-Ju Bai <baijiaju1...@gmail.com>
---
v2:
 * Add more description.
---
 drivers/usb/class/cdc-wdm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index a0d284ef3f40..632a2bfabc08 100644
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -458,7 +458,7 @@ static int service_outstanding_interrupt(struct wdm_device 
*desc)
 
        set_bit(WDM_RESPONDING, &desc->flags);
        spin_unlock_irq(&desc->iuspin);
-       rv = usb_submit_urb(desc->response, GFP_KERNEL);
+       rv = usb_submit_urb(desc->response, GFP_ATOMIC);
        spin_lock_irq(&desc->iuspin);
        if (rv) {
                dev_err(&desc->intf->dev,
-- 
2.17.0

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